intraoperative assessment of the breast arch pathol lab med—vol 129, december 2005 intraoperative...

Arch Pathol Lab Med—Vol 129, December 2005 Intraoperative Assessment of the Breast—Laucirica 1565

Intraoperative Assessment of the BreastGuidelines and Potential Pitfalls

Rodolfo Laucirica, MD

● Context.—Intraoperative evaluation of breast tissue haschanged as newer imaging techniques and surgical ap-proaches to the treatment of breast cancer have placed thepathologist in a pivotal role in the management of this dis-ease. Assessment of the index lesion and surgical marginsare but two of the many tasks we face when the specimenarrives in the surgical pathology laboratory. We are alsocalled on to correlate changes in the mammogram withthe gross pathology, particularly in those cases in whichthe lesion is nonpalpable. More recently, pathologists havebeen asked to analyze 1 or more sentinel lymph nodes atthe time of frozen section to look for metastatic disease.This review discusses many of these issues and also pro-

vides a simplified approach to the differential diagnosis ofa variety of breast lesions one may encounter intraopera-tively.

Objective.—To provide guidelines for and address po-tential pitfalls in the intraoperative management of thebreast.

Data Sources.—Author’s experience and pertinent liter-ature.

Conclusions.—Careful assessment of the gross specimencoupled with prudent utilization of frozen sections is piv-otal to reducing intraoperative error rates and preventingneedless anxiety for the patient.

(Arch Pathol Lab Med. 2005;129:1565–1574)

Regardless of the type of breast specimen sent for intra-operative consultation, the pathologist must ask 3 im-

portant questions regarding the tissue submitted for fro-zen section examination. Is there a lesion of sufficient size,such that not all the tissue will be sacrificed for intraop-erative analysis (ie, essential diagnostic material will notbe lost)? Based on the recommendations of the Directorsof Anatomic and Surgical pathology, tumors smaller than1.0 cm should not be submitted for frozen section exam-ination.1 If only an initial biopsy of a larger lesion is re-ceived, will additional material be sent for permanentevaluation? Most importantly, will my diagnosis have animmediate and relevant impact on the operative manage-ment of the patient’s breast lesion? If the answer to any ofthese questions is no, then intraoperative evaluation of thespecimen is usually not warranted. Improper utilizationof frozen sections can lead to misinformation, unnecessaryanxiety, needless additional surgical intervention, and in-creased costs. In the preoperative setting, effective com-munication between the radiologist, surgeon, and pathol-ogist will go a long way to prevent errors in the diagnosisand treatment of a variety of breast lesions.

TYPES OF SPECIMENSAt our institution, we receive various types of breast

specimens for intraoperative consultation. Depending on

Accepted for publication August 8, 2005.From the Department of Pathology, Baylor College of Medicine, Ben

Taub General Hospital, Houston, Tex.The author has no relevant financial interest in the products or com-

panies described in this article.Reprints: Rodolfo Laucirica, MD, Department of Pathology, Baylor

College of Medicine, One Baylor Plaza, Houston, TX 77030 (e-mail:[email protected]).

the mammographic and clinical findings, they include in-cisional or excisional biopsies, lumpectomies, and mastec-tomies.

Incisional Biopsies

Incisional biopsies usually represent small portions oftissue or needle cores from a palpable mass. They are usu-ally performed for 1 of 2 reasons: either an immediatediagnosis is needed so that the surgeon can proceed todefinitive surgical treatment (either lumpectomy or mas-tectomy) as a 1-stage procedure, or the patient has an in-operable tumor and lesional tissue is required for diag-nosis and hormonal analysis prior to neoadjuvant cyto-reduction chemotherapy or radiation therapy. In the lattercase, cytologic imprints (see ‘‘Special Techniques’’) of thefresh tissue, coupled with judicious sampling for frozensectioning will, in most cases, prevent freezing of the en-tire biopsy.

Excisional Biopsies

Excisional biopsies are usually performed to completelyremove a palpable or mammographically detected lesion.For mammographic lesions, a specimen radiograph (Fax-itron) is obtained (see ‘‘Gross Examination’’) and com-pared with the preoperative mammogram to ensure thatthe lesion in question is present in the biopsy. Inking ofall excisional biopsies is recommended prior to sectioningso that microscopic assessment of the margins can be per-formed. If the specimen has been oriented by the surgeon(which should be strongly encouraged), the various mar-gins can be identified using different-colored inks. Withthe increased use of stereotatic core biopsies, we now re-ceive excisional biopsies with metallic clips that are placedby the radiologist at the time of the biopsy. These speci-

1566 Arch Pathol Lab Med—Vol 129, December 2005 Intraoperative Assessment of the Breast—Laucirica

Figure 1. Composite photograph of a mucinous carcinoma of thebreast. A, Note that the tumor grossly involves the inked margin alongthe lateral edge of the breast biopsy. B, A frozen section of the tumorconfirms the positive margin (hematoxylin-eosin, original magnification3400).

Figure 2. Gross photograph of an invasive lobular carcinoma. Thetumor diffusely infiltrates the breast parenchyma in fibrous bands ratherthan forming a discrete mass. Photograph courtesy of Thomas Wheeler,MD, Houston, Tex.

mens may also be sent to the frozen section laboratory toconfirm the presence of the clip, marking the site of theprior core biopsy. Unless there is a justified reason to per-form a frozen section, excisional biopsies can be processedfor routine sectioning once the lesion of interest is iden-tified by gross or radiographic evaluation.

Lumpectomies (With or Without SentinelLymph Node Mapping)

Breast conservative surgery is rapidly replacing mastec-tomies for the surgical treatment of most breast cancers.These specimens are usually marked with sutures for ori-entation and may have a thin ellipse of skin overlying thebreast tissue. Since these patients have a preoperative di-agnosis of malignancy, a frozen section for diagnostic pur-poses is usually not needed. Under certain situations, thepathologist may freeze 1 or more of the margins from thelumpectomy specimen if the tumor grossly approximatesa particular margin. Freezing of all margins regardless ofthe proximity of the tumor should not be undertaken, asthis may yield inaccurate information, especially given thedifficulties associated with freezing and cutting adiposetissue (see ‘‘Artifacts’’).

MastectomiesMost mastectomies performed today are undertaken af-

ter a diagnosis of malignancy has been made by fine-nee-dle aspiration, core biopsy, or excisional biopsy. It is there-fore important to know the prior diagnosis before at-tempting to evaluate these specimens, since residual dis-ease may be grossly undetectable. Pathologists are usuallynot asked to perform frozen sections of mastectomy spec-imens unless there is specific margin that interests the sur-geon. In addition, the surgeon may mark the highest nodefrom the axillary dissection if it is clinically suggestive ofmetastatic disease. A frozen section of this node may berequested to confirm malignancy. Additional nodes maythen be removed at the time of surgery, if the highest nodeis positive.

GROSS EXAMINATIONMacroscopic examination of the surgical specimen is of

paramount importance, especially when deciding what, ifanything, should be submitted for intraoperative evalua-tion. All excisional biopsies should be measured, weighed,and inked before sectioning. The specimen is then se-quentially sliced at 3- to 5-mm intervals (‘‘breadloafed’’),and each slice is carefully examined.2 If a gross lesion ispresent, it should be described and measured. In addition,the distance to the nearest gross margin should also benoted (Figure 1). A frozen section should not be attemptedunless the lesion is grossly suggestive of malignancy andthe surgeon needs to remove additional tissue fromaround the biopsy site to obtain clear margins. The mac-roscopic appearances of several benign and malignantbreast lesions are listed in Table 1. Remember that well-circumscribed lesions are not always benign and stellatelesions are not always malignant. Also, invasive lobularcarcinoma frequently presents as a diffuse thickening rath-er than a distinct mass (Figure 2). Given the fact that hor-monal analysis is now routinely done by paraffin immu-nohistochemistry, we no longer need to sacrifice lesionaltissue for these ancillary studies. Sampling for permanentsections should include the tumor and adjacent breast tis-sue, uninvolved breast parenchyma, and margins. If pos-

sible, try to include a section containing the tumor in re-lation to the nearest inked margin. This will allow for ac-curate microscopic assessment of the surgical margin.

Excisional biopsies performed for nonpalpable lesions,including those associated with calcifications, require aslightly different approach. A specimen radiographshould be obtained and compared with the preoperativemammogram. Once the index lesion is identified, the


Table 1. Macroscopic Appearance of Benign andMalignant Breast Lesions

Scar or stellate lesionBenign

Fat necrosisRadial scar/complex sclerosing lesionMicroglandular adenosisGranular cell tumor

MalignantCarcinomas

Well-circumscribed/lobulated lesionBenign

Fibroadenoma and variantsPhyllodes tumorAdenosis tumorIntraductal papilloma

MalignantIntraductal papillary carcinomaMedullary carcinomaMucinous carcinomaPhyllodes tumor (low and high grade)Sarcomas

Cystic lesionBenign

Fibrocystic change

MalignantRare forms of invasive carcinoma (squamous and cystic

carcinomas)

Figure 3. Specimen radiograph of an excisional breast biopsy con-taining numerous calcifications. The tissue blocks containing the cal-cifications should be noted in the gross description, and multiple levelsof these cassettes can be requested for histologic evaluation.

Figure 4. Diagram illustrating an approach to sampling breast speci-mens for calcifications. In those cases in which the lesion is nonpalpa-ble, use the specimen radiograph as a guide for tissue sampling. Dia-gram courtesy of Syed Mohsin, MD, Columbus, Ohio.

specimen should be serially sectioned and placed in par-affin blocks in such a manner as to maintain its properorientation. The cassettes should then be radiographed, sothat the block(s) with the index lesion can be identified(Figure 3). In this manner, the pathologist can correlatethe gross and histologic findings with the preoperativemammogram. The entire lesion along with the peripheraland end margins should be submitted for microscopicevaluation. Portions of breast tissue between the index le-sion and the excision margins should also be submittedfor pathologic assessment. If the specimen is complicatedand requires extensive sampling of several areas, a dia-gram of the specimen should be made, delineating wherethe tissue sections were obtained (Figure 4).

When no discrete lesion is present, some laboratoriesadvocate processing the entire specimen for pathologic ex-amination. Remember, given the economic pressures un-der which we currently practice, we need to balance pru-dent sampling of the specimen with laboratory costs with-out compromising patient care. To resolve this issue, cri-teria have been established for sampling of grosslyunremarkable breast biopsies.3 Schnitt and Wang3 retro-spectively analyzed 384 specimens entirely submitted forhistologic examination from biopsies performed for clini-cally palpable lesions in which no distinct tumor was ev-ident on gross examination. They concluded that signifi-cant lesions (ie, carcinomas and atypical hyperplasias)were identified in fibrous tissue when up to 10 cassetteswere submitted per case. This also resulted in an 18%reduction in the number of blocks needed for each biopsy.Based on these findings, the authors recommended sub-mitting up to 10 tissue blocks of fibrous parenchyma and/or fat for each biopsy. If carcinoma or atypical hyperplasiais identified in the initial slides, the remaining tissue may


be processed to look for additional foci of malignancy oratypical hyperplasia.

Lumpectomies should be grossed in a manner similarto excisional biopsies. Remember that the margins shouldbe inked, using multiple colors if necessary. If a portionof skin is present, it should also be inked and sampled forhistologic evaluation. Lumpectomies associated with sen-tinel lymph node mapping can usually be grossed within24 hours of the surgery without fear of significant radia-tion exposure, provided the specimen is adequately fixed.Studies have shown that surgeons performing sentinellymph node mapping and biopsy have minimal radiationexposure. The data state that the expected radiation ex-posure to a surgeon during a 3-hour sentinel node pro-cedure on a patient administered 20 mCi of technetium-99m sestamibi is approximately 1 mrem. For comparison,the acceptable radiation limits to radiation workers is 5000mrem per year, and for nonradiation workers it is 500mrem per year.4 From these data, one can extrapolate thatthe risk for pathologists handling these specimens is evenlower than the risk for the surgeon, given the time thathas elapsed since administration of the radioactive solu-tion and the specimen’s arrival in the surgical pathologylaboratory. Radiation counts performed at 1 of our affili-ated teaching hospitals support the negligible exposure topathologists handling these specimens. Counts of the sen-tinel node and breast specimen were less than 2 mreminitially and 0 mrem the following day (;12–15 hourspostoperatively). Gross evaluation of sentinel lymph nodeswill be discussed under the heading of ‘‘Special Tech-niques.’’

Mastectomies should be weighed, measured, and inkedprior to sectioning. After performing the gross or intra-operative frozen section consultation, the specimen shouldbe serially sectioned at 3- to 5-mm intervals and placed informalin for several hours before sections are taken forhistologic evaluation. This will ensure that the adipose tis-sue is adequately fixed before processing of the tissue sec-tions. In most cases, when a mastectomy specimen is sentto the frozen section laboratory, the surgeon is usuallyinterested in the deep resection margin relative to the bi-opsy site or any residual tumor that is grossly present. Ifno residual tumor is grossly present, then 4 to 8 sectionsof the biopsy site (to include the deep margin) should beobtained. Two to 3 sections from each of the 4 quadrantsare usually sufficient, if no additional lesions are seen. Theskin overlying the biopsy site and nipple/areolar complexshould also be sampled. The axillary tail can be arbitrarilydivided into thirds, relative to the adjacent breast, forlymph node dissection. If the surgeon has tagged thehighest lymph node, it should be submitted separately. Inselected cases, gross photographs should be obtained fordocumentation and teaching purposes. Finally, given thenationwide push for standardization of surgical pathologyreports, I am including the College of American Patholo-gists Web address for those who may want to downloadthe surgical pathology protocol checklists for breast andother organ sites.5

SPECIAL TECHNIQUES

Intraoperative Cytology

Cytologic preparation of the tumor at the time of intra-operative consultation is a useful adjunctive technique thatcomplements frozen section analysis of the tumor. Frozen

section artifacts that may impair morphologic assessmentof the tumor can largely be avoided if cytologic materialis also available for analysis. Smears can be prepared in 1of 3 ways: (a) cytologic imprints, in which the tumor isdirectly pressed against a slide; (b) squash preparations,in which a 1-mm fragment of tumor is gently pressed be-tween 2 slides; or (c) scrape preparations, in which a cleanscalpel is scraped along the tumor surface and the mate-rial is then transferred and smeared onto a slide. The lattertechnique is quite useful when the tumor is highly fibrotic.No matter which technique is used to obtain the cytologicmaterial, it is imperative that the material is immediatelyfixed in ethanol for maximum preservation of the cellulardetail (Figure 5).

Sentinel Lymph Node MappingSentinel lymph node mapping is now performed on se-

lected patients who opt for conservative surgery to treattheir breast cancer. The procedure involves the surgicalidentification of those axillary lymph nodes that theoreti-cally would be the first ‘‘sentinel’’ nodes to receive thelymphatic drainage from the breast harboring the invasivecancer. If these nodes are pathologically negative, the pa-tient is spared the morbidity associated with a standardaxillary node dissection. Surgical identification is based onthe peritumoral injection of radioactive solutions and/orcolored dyes. The surgeon then massages the breast tofacilitate permeation of the solution into the lymphatic sys-tem. Several hours after the injection, the patient is takento the operating room, where the surgeon uses a radio-active counter to locate the ‘‘hot’’ lymph node. If a coloreddye has been used, visual inspection of the axilla usuallyidentifies the sentinel lymph node (Figure 6). Usually, thepathologist receives 1 to 3 lymph nodes for evaluation.Some centers use cytologic imprints (see ‘‘IntraoperativeCytology’’), either with or without frozen section evalua-tion, at the time of surgery to determine whether the sen-tinel node is involved by metastatic tumor.6,7 If the im-prints are positive, then the surgeon proceeds to an axil-lary node dissection. Other hospitals submit their sentinellymph node biopsies for routine processing without intra-operative consultation. Once the specimen is received inthe pathology laboratory, the pathologist must carefullydissect out all the nodes and record the number and sizes.If it is technically feasible, each node should be seriallysectioned at 2- to 3-mm intervals, parallel to the long axis,and entirely submitted for evaluation. One hematoxylin-eosin–stained section should be cut from each block forlight microscopy (Figure 7). Additional unstained levelsmay also be requested at the time of sectioning, in theevent that immunohistochemical analysis of the node willbe required to confirm the diagnosis of metastatic disease.Although some studies advocate using immunohisto-chemistry on all histologically negative lymph nodes,4 thecurrent College of American Pathologists guidelines statethat this procedure is not the standard of care for patho-logic evaluation of sentinel lymph nodes in patients withinvasive breast cancer.8

FROZEN SECTION EXAMINATIONThe percentage of breast specimens evaluated by frozen

examination appears to have decreased over the years asnew diagnostic modalities have altered the clinical man-agement of breast lesions. Review of our data from BenTaub Hospital (Houston, Tex) seems to support this con-


Figure 5. Composite photograph of an invasive, no special type (ductal) carcinoma. A, Cytologic preparation of the tumor at the time of frozensection. There are loosely cohesive groups and single cells that display cytologic features of malignancy (hematoxylin-eosin, original magnification3400). B, The corresponding frozen section of the tumor is depicted in this photograph (hematoxylin-eosin, original magnification 3400). Notethat the cellular and nuclear detail of the malignant cells is better preserved in the cytologic material.

Figure 6. An intraoperative photograph of a sentinel lymph node biopsy. Note the blue dye in the sentinel nodes and surrounding lymphaticchannels. Photograph courtesy of Anthony Lucci, MD, Houston, Tex.

Figure 7. Sentinel lymph node with metastatic breast cancer. The tumor is present in the subcapsular sinus of the involved node (hematoxylin-eosin, original magnification 3200). This patient subsequently underwent an axillary node dissection.

clusion. Between 1985 and 1995, 20% to 35% of all intra-operative consultations sent to the frozen section labora-tory were from the breast. However, during the last 3years, this percentage has decreased to 4% to 8%. In ad-dition, there has been a change in the type of specimensubmitted for frozen section evaluation. Currently, mostcases are related to intraoperative evaluation of resectionmargins, rather than the index lesion. These changes re-flect a shift in the current management of breast lesions,with more patients being evaluated in the preoperativesetting with either fine-needle aspiration or core biopsy.Also, a larger number of women are presenting with non-palpable disease, given the widespread use of screeningmammography in women older than 40 years. As withany other test performed in the laboratory, there is an in-herent false-positive and false-negative rate. Data from theliterature report that the percentage of false-positive fro-zen section diagnoses of breast lesions varies from 0.03%to 0.1%, and the rate of false-negative diagnoses variesfrom 0.5% to 1.0%. Frozen section diagnosis is deferredin 0.5% to 3% of all breast biopsies.9,10

A large retrospective analysis of frozen section diag-noses from a teaching hospital documented that diagnos-

tic errors related to intraoperative consultations can belargely divided into the following 4 groups: those result-ing from interpretation (57%), microscopic sampling(24%), gross sampling (9.5%), and lack of communicationbetween the pathologist and surgeon (9.5%).11 Althoughmeticulous gross and microscopic evaluation can go a longway to reduce errors related to sampling, errors cannot betotally eliminated, especially when dealing with largespecimens for which freezing the entire lesion is not jus-tified. Also, it is important that the pathologist keep amental note of the size of the tissue sample that is beingsubmitted for intraoperative consultation; this way, he orshe can be certain that the entire surface of the lesion issampled for histologic examination. Interpretative errorsmay result from artifacts of the freezing procedure (see‘‘Artifacts’’ below) and/or inexperience on the part of thepathologist interpreting the slide. If there is any doubt orconcern on the part of the pathologist who is interpretingthe frozen section, this issue must resolved before—notafter—the intraoperative diagnosis is given. There is noroom for what if’s or maybe’s once you have received themastectomy specimen in the surgical pathology laborato-ry. Finally, in cases in which there is an equivocal or de-


Figure 8. This photograph depicts one problem associated with mar-gin assessment of breast specimens. Given the irregular surface ofbreast tissue, the dye has a tendency to spread between the lobules offibroadipose tissue. This creates ‘‘false’’ margins relative to the invasivecarcinoma shown in the lower half of this photograph (hematoxylin-eosin, original magnification 320).

ferred diagnosis, this information needs to be clearly com-municated to the surgeon so that appropriate intraopera-tive measures can be taken (eg, additional tissue).

INDICATIONS

Establish a Diagnosis of a Breast Lesion Prior toDefinitive Therapy

Today, most malignant breast lesions are diagnosed pri-or to the definitive surgical therapy (ie, lumpectomy ormastectomy), either by fine-needle aspiration or stereotac-tic core biopsy. However, in certain instances, the surgeonand/or patient may request that the initial diagnostic bi-opsy and definitive treatment be undertaken simulta-neously. Frozen section evaluation of a breast lesion mayalso be performed when the fine-needle aspiration or corebiopsy results are equivocal.

Evaluation of Resection Margins

Although careful gross examination of the breast spec-imen is usually all that is required to assess margin status,if the tumor closely approximates a specific margin, a fro-zen section of that margin should be done so that the sur-geon can obtain clear margins before completing the op-eration. Intraoperative evaluation of all the margins shouldnot be done, especially if the gross examination does notshow tumor near the inked margin. If frozen sections ofthe margins are not needed, then the pathologist should

tell the surgeon the gross distance of the tumor to theclosest margin. This way, the surgeon can decide if addi-tional tissue should be removed from the margin in ques-tion. Remember that breast tissue does not have a smoothouter surface; therefore, the dye used to ink the marginsmay spread between the lobules of fibroadipose tissue,making it difficult to determine the ‘‘true’’ resection mar-gin (Figure 8).

Given the fact that prognostic markers (estrogen recep-tor, progesterone receptor, HER-2/neu) are currently eval-uated by paraffin immunohistochemistry, freezing of tu-moral tissue for analysis of these markers is no longerrequired.

ARTIFACTS

Artifacts that may impede intraoperative evaluation ofbreast specimens may originate from the operative pro-cedure or the frozen section laboratory. Electrocautery in-struments used to remove breast tissue may cause exten-sive thermal damage to the specimen. The most significanteffect is severe alteration in the architectural and cytologicdetail of the epithelial cells, making it difficult to evaluateepithelial proliferative lesions or to separate benign pro-cesses such as sclerosing adenosis from invasive carcino-ma. Because the diathermy effect is maximal at the edgesor marginal surfaces of the tissue, electrocautery artifactsseverely limit the assessment of the margins of excision(Figure 9). In addition, if the electrocautery instrumenttransects the tumor, this may alter receptor activity and/or hamper the diagnosis or classification of the tumor.12

Crush artifacts may also hamper the frozen diagnosis ofa tumor. This issue may arise when the surgeon obtains acore biopsy to confirm the diagnosis of cancer before at-tempting either a lumpectomy or mastectomy. Given thedifficulty of assessing crushed cells in a frozen section, itis best to request additional material before rendering adiagnosis of malignancy. Figure 10 illustrates an exampleof crushed tumor cells in a core biopsy. Fortunately, di-agnostic material was present in one of the other cores.

In the frozen section laboratory, technical problems re-lated to the freezing procedure, tissue, or staining meth-odology may hamper the intraoperative diagnosis. Care-ful selection of the tissue sample is an important first stepwhen performing a frozen section. Large samples tend tofreeze slowly, thereby causing the formation of ice crystalsin the specimen. Also, improper freezing of the specimenmay create artifactual spaces around tumor nests that maybe erroneously diagnosed as lymphatic or vascular inva-sion. We all know the difficulty involved in freezing andcutting adipose tissue. Unfortunately, this problem cannotbe completely circumvented when freezing breast tissue.When feasible, try to trim off as much adipose tissue aspossible before submitting the sample for intraoperativeanalysis. Sometimes cutting the specimen at a slightlyhigher thickness (8–10 mm) may help both in sectioningand keeping the tissue on the slide. Properly stained sec-tions begin with adequate fixation. Therefore, one mustplace the cut sections into the ethanol as quickly as pos-sible so that the cells are immediately fixed, thereby pre-serving the cellular detail. Most laboratories, includingours, use a rapid hematoxylin-eosin stain for intraopera-tive analysis. Given that hematoxylin is a water-basedstain, removal of all the ethanol is a crucial first step toprevent understaining of the tissue sections. Also, filtering


Figure 9. Composite photograph depicting the diathermy effect at the edge of a breast biopsy. A, The cautery artifact has markedly distorted theepithelial cells within this lobular unit (hematoxylin-eosin, original magnification 3200). B, Given the smudged and elongated appearance of theductal epithelium, the degree of atypia cannot be determined accurately in this proliferative lesion. The cauterized margin is present along thelower right corner of this picture (hematoxylin-eosin, original magnification 3400).

Figure 10. Crushed tumor cells in a core biopsy of an invasive carcinoma. Although there appears to be an infiltrative pattern in this lesion, theextensive crush artifact precludes accurate evaluation of the cytologic detail of these cells (hematoxylin-eosin, original magnification 3400).

Figure 11. Composite photograph of sclerosing adenosis from a patient with extensive fibrocystic changes. A, There are several compressedductal structures that exhibit pseudoinvasion between acini of a terminal duct lobular unit (hematoxylin-eosin, original magnification 3400). B,A second focus photographed at a lower power demonstrates the characteristic lobulocentric distribution of sclerosing adenosis (hematoxylin-eosin, original magnification 3100).

Figure 12. Frozen section of a breast biopsy containing a radial scar. This lesion was found on mammography and reported as suspicious formalignancy. Note the central elastosis and peripheral distribution of several sclerotic and hyperplastic lobular units associated with microcalcifi-cations (hematoxylin-eosin, original magnification 340).


Figure 13. Fibroadenoma excised from a 23-year-old woman. The diagnosis of a fibroadenoma is usually not a diagnostic problem on frozensection. The characteristic intracanalicular growth pattern is evident in this photograph (hematoxylin-eosin, original magnification 340).

Figure 14. Phyllodes tumor removed from a 46-year-old woman. The typical leaflike processes of this tumor is evident in this picture. As notedin the text, one should not try to subclassify these tumors on frozen section. A generic term, such as fibroepithelial lesion may be used pendingfurther histologic sampling (hematoxylin-eosin, original magnification 320).

Figure 15. Tubular carcinoma. There is haphazard arrangement of the tubules in a desmoplastic stroma. Some of the tubules have angulatedcontours and are lined by a single row of cells (hematoxylin-eosin, original magnification 3400).

Figure 16. Invasive lobular carcinoma involving 2 ductal structures. Note the characteristic targetoid growth pattern surrounding the upper duct(hematoxylin-eosin, original magnification 3400).

Table 2. Differential Diagnosis Between Sclerotic Breast Lesions and Tubular Carcinoma

Histologic Characteristics Radial Scar Sclerosing Adenosis Sclerosing Papilloma Tubular Carcinoma

Glandular architectureFibrous reactionMarginsGlandular components

HaphazardCentralInfiltrativeDouble layer

LobulocentricWithin lobuleRoundedDouble layer

NodularWithin papillomaRoundedDouble layer

HaphazardEvenly distributedInfiltrativeSingle layer

the stains is important for staining clarity and preventionof ‘‘tissue floaters’’ from other cases.

HISTOPATHOLOGY

A simple approach to the different lesions encounteredin frozen sections of breast specimens is to subcategorizethem into the following diagnostically useful groups: be-nign lesions mimicking cancer, fibroepithelial lesions, in-vasive carcinomas, and those lesions that fall in the cate-gory of ‘‘deferred diagnosis.’’ The following paragraphsdiscuss the more common examples in these variousgroups and their associated morphologic pitfalls.

Benign Lesions Mimicking CancerOverdiagnosis of this group of lesions can lead to di-

sastrous consequences for the patient. They include radialscars/complex sclerosing lesions, sclerosing adenosis, andsclerosing papillomas. These lesions may result in a mis-taken diagnosis of malignancy because irregularly shapedglands entrapped within dense fibrous tissue appear toinfiltrate the breast parenchyma (‘‘pseudoinvasion’’). Theoccasional presence of glands within perineural spaces inradial scars/complex sclerosing lesions and sclerosing ad-enosis also adds to the diagnostic confusion. The presenceof a 2-cell layer in these entrapped ducts is a useful mor-


Figure 17. Epithelial proliferative lesions. A, Florid usual ductal hyperplasia on frozen section. Streaming of the epithelial cells, the irregularspaces, and heterogenous appearance of the ductal cells are morphologic signs of benignity (hematoxylin-eosin, original magnification 3200). B,Atypical ductal hyperplasia. Three ductal structures are replaced by proliferative lesions exhibiting a greater degree of architectural and cytologicatypia when compared with part A (hematoxylin-eosin, original magnification 3200).

Figure 18. Ductal carcinoma in situ. This patient presented with mammographic and clinical findings that were highly suspicious for malignancy.A frozen section revealed extensive high-nuclear-grade ductal carcinoma in situ associated with necrosis and calcifications. A focus of invasivecarcinoma was identified in the permanent sections (hematoxylin-eosin, original magnification 3200).

Figure 19. Atypical papillary lesion. Frozen section from a complex cystic lesion in an elderly woman. The papillary fronds are lined by pseu-dostratified and papillary tufts of epithelial cells along the right half of the photograph. A cribriform-like area is present near the center. Thearchitectural and cytologic findings are worrisome for an intracystic (intraductal) papillary carcinoma. This finding was confirmed in the permanentsections. No invasive carcinoma was found (hematoxylin-eosin, original magnification 3200).

Figure 20. Malignant lymphoma of the breast. This touch imprint is from a 61-year-old woman with a prior diagnosis of non-Hodgkin lymphoma. Amonomorphic population of atypical lymphoid cells is seen. A few multilobated forms and mitotic figures are also present. Flow cytometric studiesrevealed a monoclonal B-cell lineage, confirming the diagnosis of non-Hodgkin lymphoma (hematoxylin-eosin, original magnification 3400).


phologic clue to their benign nature. Other distinguishingfeatures include the lobulocentric nature of the glandularproliferation in sclerosing adenosis, central elastosis andperipheral radiating ducts in radial scars/complex scle-rosing lesions, and papillary projections and dilated spac-es seen along the periphery of sclerosing papillomas (Fig-ures 11 and 12). Table 2 summarizes the salient featuresof these sclerotic proliferative lesions. Other less commonentities that should not be attempted on frozen sectioninclude microglandular adenosis, tubular adenosis, andgranular cell tumors.13,14

Fibroepithelial LesionsThis category includes fibroadenoma and phyllodes tu-

mor. Frozen section evaluations of fibroadenomas usuallydo not present diagnostic problems (Figure 13). However,differentiating a cellular fibroadenoma from a phyllodestumor may be almost impossible to do on a frozen section,given the extensive sampling that may be needed to sep-arate these 2 entities. In such cases, the generic diagnosisof ‘‘fibroepithelial lesion’’ is preferred. It also may not bepossible to differentiate a low- versus high-grade phyl-lodes tumor based on the frozen section result, since nu-merous histologic parameters such as tumor border, stro-mal cellularity, stromal overgrowth, and mitotic activityneed to be assessed in several permanent sections of thetumor.15 Again, the intraoperative diagnosis of fibroepi-thelial lesion should be used with the caveat that this mayturn out to be a phyllodes tumor on the permanent sec-tions (Figure 14). This way, additional tissue can be ex-cised from the margins at the time of the initial surgery,if the diagnosis of phyllodes tumor is a likely possibility.

Invasive CarcinomasIn most instances, identifying a breast carcinoma as in-

vasive is not difficult. The main histologic feature of inva-sion is the totally disorganized arrangement of the neo-plastic cells in association with a desmoplastic stromal re-action. There are, however, certain forms of invasive cancerthat may present diagnostic challenges at the time of frozensection. They include tubular carcinoma and the classicform of invasive lobular carcinoma. Tubular carcinomasconsist of haphazardly arranged small glands and angu-lated tubules formed by a single layer of neoplastic cells(Figure 15). The differential diagnosis includes sclerosingadenosis. As mentioned previously, the glandular prolifer-ation in sclerosing adenosis has a lobulocentric pattern atlow power, and the glands are formed by 2 rows of cells(inner epithelial and outer myoepithelial layer). Table 2summarizes the morphologic features of tubular carcinomaversus the sclerotic proliferative lesions that mimic invasivecancer. Invasive lobular carcinoma is often misdiagnosedbecause of the paucicellular nature of the tumor, coupledwith the bland nuclear features of the neoplastic cells. Thelinear and targetoid growth patterns of this tumor are help-ful histologic clues for diagnosis (Figure 16). Given thesmall size of the tumor cells, they may be mistaken forchronic inflammatory cells. Cytologic smears are a usefuladjuvant in this differential diagnosis. With invasive lobularcarcinoma, one will see cellular cohesion and intracyto-plasmic mucin droplets in the neoplastic cells. When facedwith an unusual or rare form of invasive breast cancer, ageneric diagnosis of invasive carcinoma can be used at thetime of frozen section, with the final diagnosis pendinghistologic sampling of the fixed tissue.

Deferred Diagnosis

Although one should make every attempt to arrive at aspecific diagnosis at the time of frozen section, there areinstances in which it would be prudent not to do so. Allepithelial proliferative lesions should not be diagnosed bymeans of a frozen section. That includes usual ductal hy-perplasia, atypical ductal and lobular hyperplasia, and duc-tal and lobular carcinoma in situ (Figure 17). With the ex-ception of comedo-type ductal carcinoma in situ, these le-sions rarely, if ever, present as a palpable mass requiringintraoperative analysis (Figure 18). Overcalling atypicalductal hyperplasia at the time of frozen section may causethe patient to suffer needless anxiety. Papillary epitheliallesions also should not be diagnosed intraoperatively. Thedifferential diagnosis between an intraductal papillomaand papillary carcinoma is based on extensive sampling ofthe fixed tissue, looking for a single layer of epithelial cellsin the latter diagnosis. If the mammographic and/or clin-ical findings suggest that the papillary lesion has a highprobability of being malignant, then complete excision ofthe lesion with ample surgical margins should be attempt-ed as a 1-stage procedure (Figure 19). Lymphoproliferativelesions that involve the breast should be handled in a man-ner similar to lymph node biopsies performed for suspect-ed lymphoma. If the cytologic and/or frozen section is sug-gestive of non-Hodgkin lymphoma, fresh tissue should besaved for possible flow cytometric studies. Figure 20 illus-trates a rare case of non-Hodgkin lymphoma involving thebreast. A final diagnosis of B-cell lymphoma was made af-ter correlating the morphology with the flow cytometricstudies. Finally, intraoperative diagnosis of soft tissue tu-mors should also be deferred. This would include entitiessuch as pseudoangiomatous stromal hyperplasia, fibroma-tosis, and vascular and mesenchymal tumors.

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