jurnal radiologi

262 AJR:202, February 2014

Imaging of Breast Cancer–Related Changes After Surgical Therapy

Colleen H. Neal1 Zeynep N. Yilmaz1 Mitra Noroozian1 Katherine A. Klein1 Baskaran Sundaram2

Ella A. Kazerooni2

Jadranka Stojanovska2

Neal CH, Yilmaz ZN, Noroozian M, et al.

1Department of Radiology, University of Michigan Health System, Ann Arbor, MI.

2Department of Radiology, Division of Cardiothoracic Radiology, University of Michigan Health System, UH B1-132 Taubman/Box 0302, 1500 E Medical Center Dr, Ann Arbor, MI 48109-0302. Address correspondence to J. Stojanovska ([email protected]).

Women’s Imaging • Review

This article is available for credit.

AJR 2014; 202:262–272

0361–803X/14/2022–262

© American Roentgen Ray Society

Keywords: breast cancer, chest CT, hematoma, postsurgical changes, seroma

DOI:10.2214/AJR.13.11517

Received July 1, 2013; accepted after revision September 9, 2013.

Presented in part at the 2012 annual meeting of the Association of University Radiologists.

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ologist should be familiar. In this article, we review thoracic CT manifestations of breast cancer surgical treatment correlated with multimodality imaging, such as mammogra-phy, breast ultrasound, breast MRI, and PET. The spectrum of postoperative changes attrib-uted to each surgical approach and surgery-re-lated complications will be reviewed.

Breast Conservation SurgeryBreast conservation surgery includes

lumpectomy, partial mastectomy, and seg-mentectomy. The aim of breast conservation surgery is surgical excision of breast cancer with a surrounding margin of histological-ly benign breast parenchyma while conserv-ing the patient’s breast appearance and form. Breast conservation surgery is the most com-mon surgical option for patients with early-stage breast cancer, typically T1 or T2. It is performed as part of a multidisciplinary ap-proach to breast cancer treatment that most commonly includes postoperative radiation and possibly adjuvant chemotherapy. Pa-tients who are not candidates for postoper-ative radiation (i.e., pregnancy, prior chest wall radiation) are not typically treated with breast conservation surgery as their definitive cancer surgery. Lumpectomy followed by breast radiation has replaced modified radical mastectomy as the preferred treatment of ear-

In the United States, breast cancer is the second leading cause of cancer mortality in all women and the leading cause of mortality for

women under 50 years old [1]. It is estimated that 207,090 women in the United States are diagnosed with breast cancer each year. In the past 20 years, breast cancer mortality has con-tinued to decrease in the United States [1], likely due to improved treatment and imple-mentation of screening mammography. In fact, 89% of women with a history of breast cancer are breast cancer survivors [1]. These patients have most often been treated with a combination of surgical resection, radiation therapy, and possibly chemotherapy. There are several surgical options offered to breast cancer patients in terms of definitive cancer surgery and reconstruction. The surgical treat-ment recommendation may depend on the stage of the cancer, age of the patient when the cancer is diagnosed, tumor histology, racial or ethnic differences, and patient preference.

Thoracic CT is commonly performed in breast cancer patients for staging and surveil-lance. In addition, thoracic CT may be indi-cated for symptoms, such as chest pain or shortness of breath, or in the evaluation of treatment-related complications. Breast can-cer treatment can result in thoracic imaging abnormalities with which the interpreting radi-

OBJECTIVE. The purpose of this article is to discuss the surgical treatment of breast cancer and its resultant thoracic CT and multimodality imaging manifestations.

CONCLUSION. Many breast cancer patients undergo cross-sectional imaging at some point during or after treatment. Thoracic CT is an important modality performed for staging and surveillance. Thoracic CT examinations often show findings related to patients’ surgical or adjuvant treatment. The postsurgical changes visible on thoracic CT may include those related to lumpectomy, mastectomy, breast reconstruction, and axillary surgery. Postsurgical compli-cations may also be seen, including fluid collections, infection, fat necrosis, and lymphedema. Recognition and appropriate interpretation of the posttherapeutic spectrum of findings are im-portant to avoid unnecessary diagnostic imaging and minimize patient anxiety.

Neal et al.Imaging Breast Cancer After Surgery

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AJR:202, February 2014 263

Imaging Breast Cancer After Surgery

ly-stage breast cancer [2]. Clinical trials have shown that breast conservation surgery fol-lowed by whole-breast tangential-beam radi-ation therapy can be as effective as modified radical mastectomy for the treatment of ear-ly-stage breast cancer, with similar survival [2, 3]. Contraindications to breast conserva-tion surgery may include multicentric or dif-fuse disease, persistent positive surgical mar-gins, prior breast irradiation, unfavorable tumor-to-breast size ratio, and pregnancy be-cause of the subsequent radiation therapy [4]. When feasible, the conservative approach of breast conservation surgery may be favored to preserve patient quality of life [5]. Sentinel lymph node biopsy with or without axillary lymph node dissection is usually performed

through a different incision than the defini-tive breast conservation surgery [6].

Posttreatment imaging for a breast conser-vation surgery patient will frequently show surgical clips and distortion at the surgical site as well as overlying skin retraction (Fig. 1). Surgical clips are often placed at the time of surgery to designate the surgical site for radiation planning purposes [7, 8]. Skin and trabecular thickening can also be seen sec-ondary to radiation therapy [9].

MastectomyHistorically, the classic Halsted radical mas-

tectomy was the first surgical procedure used to treat patients with breast cancer. However, in the past decades, this procedure has been

replaced by the modified radical mastectomy. More recently, in an effort to maintain cosme-sis and patient quality of life, skin- and nipple-sparing mastectomies have been introduced as a possible option for women deemed to have oncologically safe tumors. The postoperative appearance of the chest wall on thoracic CT varies according to the mastectomy method. In radical mastectomy, the breast, pectoralis major and minor muscles are completely re-moved, leaving a bare chest wall. Regional lymph nodes along the axillary vein up to the costoclavicular ligament (levels I, II, and III axillary lymph nodes) are also removed. An extended radical mastectomy involves the ad-ditional excision of internal mammary lymph nodes, requiring a deeper incision into the

A

Fig. 1—45-year-old woman with breast cancer who had normal posttreatment appearance after lumpectomy and radiation therapy.A and B, Craniocaudal (A) and mediolateral (B) mammograms show surgical clips, architectural distortion, and skin retraction in upper mid left breast (arrows). Radiopaque circles on A and B are mole markers.C, Axial chest CT image shows surgical clips and architectural distortion in left breast (arrow). Skin thickening may also commonly be seen in treated breast.

CB

Fig. 2—68-year-old woman with history of multifocal invasive ductal carcinoma of left breast. Axial contrast-enhanced chest CT image shows posttreatment changes of left modified radical mastectomy and prophylactic right modified radical mastectomy. Breast tissue is absent and major and minor pectoralis muscles are preserved (arrows).

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chest wall; however, this procedure is no lon-ger performed because it failed to show im-proved clinical outcome [10].

The modified radical mastectomy (MRM), on the other hand, combines simple mastec-tomy with removal of axillary lymph nodes in continuity with the mastectomy specimen. MRM removes the breast tissue, leaving the pectoralis muscle intact as a cover over the chest wall (Fig. 2).

There are two forms of MRM. The first was described by Patey and Dyson [11] with a modification described by Scanlon and Cap-rini [12]. The second form of MRM was de-scribed by Auchincloss [13]. The Patey MRM preserves the pectoralis major muscle, but re-moves the pectoralis minor muscle, level I, II, and III (apical) axillary lymph nodes. A disad-vantage of the Patey procedure is potential in-jury to the pectoral nerves, resulting in atrophy of the pectoralis major muscle. Scanlon and Caprini modified the Patey MRM by dividing but not removing the pectoralis minor muscle. This method also allowed for the removal of the level III nodes with less chance of nerve

injury and pectoralis muscle atrophy [12]. In contrast, the Auchincloss MRM leaves the pectoralis minor muscle intact. This approach does limit the removal of the level III axillary nodes. However, it is not detrimental to most patients’ survival; Auchincloss found that only 2% of breast cancer patients are known to ben-efit from removal of the level III nodes [13].

Skin-sparing mastectomy (SSM) is a rel-atively new surgical approach. Breast tissue is removed but the natural skin envelope of the breast is preserved to facilitate immedi-ate breast reconstruction and improved cos-mesis [14]. It is thought to be clinically effec-tive in patients with T1 or T2 breast cancers, ductal carcinoma in situ (DCIS), and prophy-lactic mastectomies. However, SSM is contra-indicated in women with inflammatory breast cancer, skin involvement by tumor, or skin tethering [15]. SSM is performed via periare-olar incision with dissection of the breast tis-sue from the overlying subcutaneous fat, der-mis, and epidermis [14, 16]. The breast tissue, nipple, and areola are removed with the breast skin envelope remaining. Sentinel lymph node biopsy or axillary lymph node dissection can be performed at the same time as SSM. Poten-tial complications of SSM include skin necro-sis and locoregional recurrence. Concern for locoregional recurrence stems from potential involvement of skin flaps with residual tumor [15], emphasizing the importance of patholog-ic evaluation for negative superficial surgical margins. Overall, however, the locoregional recurrence rate of SSM is comparable to MRM and nonskin-sparing mastectomy [16]. Adju-

vant radiation therapy following SSM can be complicated by fat necrosis, fibrosis [14], and compromise of the reconstructed breast [16].

A modification of the SSM with preservation of the nipple-areola complex is known as the nipple-sparing mastectomy (NSM). The nipple-areola complex is recognized as a signature of breast identity [17] in women, prompting the development of the NSM technique in an ef-fort to maintain patient quality of life. NSM has been used for prophylactic mastectomy in se-lected high-risk patients. It has been used as de-finitive breast cancer surgical treatment in high-ly selected patients because the oncologic safety of NSM remains controversial [18]. Tumor size and tumor distance from the nipple are the most influential factors regarding the safety of NSM. The best available evidence suggests that NSM may be most appropriate for patients with tu-mor size smaller than 2.5 cm, nipple-to-tumor distance of more than 4 cm, no lymphovascu-lar invasion or extensive intraductal component on core biopsy, no axillary lymph node enlarge-ment on physical examination and imaging, and nonsmokers [17]. Therefore, mammography, ultrasound, and possibly breast MRI are crucial in the evaluation of potential NSM candidates for purposes of establishing tumor size and tu-mor distance from the nipple. Nipple necrosis and nipple insensitivity are major complications of NSM [17, 18]. To date, no randomized con-trolled trials have evaluated the oncologic safe-ty of NSM versus breast conservation surgery.

Both NSM and SSM necessitate immedi-ate reconstruction, which can be initiated with the placement of an expander at the time of

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Fig. 3—46-year-old woman treated with bilateral mastectomies and implant reconstruction for invasive ductal carcinoma.A–C, Axial (A and B) and sagittal (C) contrast-enhanced chest CT images show bilateral subpectoral breast implants (arrows, A and C) that are also laterally beneath serratus anterior muscle (arrowhead, B). Right pleural-based masses with loculated pleural fluid extending into major fissure represent metastatic breast cancer.

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Fig. 4—48-year-old woman with right multifocal ductal carcinoma in situ (DCIS) diagnosed 5 years earlier with normal postoperative appearance after right modified radical mastectomy with transverse rectus abdominis muscle (TRAM) reconstruction. Patient had new multifocal DCIS of left breast, which was treated with left modified radical mastectomy.A, Contrast-enhanced chest CT image shows thin soft-tissue attenuation line (arrow) that demarcates juncture between abdominal wall fat used in TRAM flap and residual subcutaneous fat after right mastectomy. There is also left modified radical mastectomy with preservation of pectoralis muscles.B, Contrast-enhanced CT image of upper abdomen shows absence of right rectus abdominis muscle (arrow), which was used to reconstruct right breast.C and D, Craniocaudal (C) and mediolateral oblique (D) mammograms show fat density of reconstructed right TRAM and surgical clips. Note curvilinear soft-tissue band that demarcates reconstructed flap from minimal residual subcutaneous fat of breast (arrows).E and F, Coronal oblique (E) and axial (F) maximum-intensity-projection images show expected mobilization of right superior epigastric artery and harvested right inferior epigastric artery feeding flap (arrows) compatible with postoperative anatomy.

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mastectomy. Other than the presence of a nip-ple in an NSM patient, there is no specific im-aging appearance on cross-sectional imaging that would distinguish an SSM or NSM pa-tient from an MRM patient if the MRM pa-tient undergone breast reconstruction.

Breast ReconstructionThere are several options for breast recon-

struction including breast prostheses (im-plants); myocutaneous flaps, such as latis-simus dorsi flap and the transverse rectus abdominis myocutaneous (TRAM) flap; and muscle-sparing free-flap autologous recon-struction, such as the deep inferior epigastric perforator (DIEP) flap. Breast prosthesis re-construction involves the initial placement of an expander implant, typically underneath the pectoralis major muscle and laterally be-neath the serratus anterior muscle (Fig. 3) to stretch out the skin and tissues. Over the sub-sequent months, the expander is injected with fluid to gradually stretch the overlying skin. An implant is then placed at a later surgery. Starting immediate reconstruction at the time of mastectomy may offer the patient signifi-cant benefit, both cosmetically and function-ally. There is practice variation in the tim-ing of reconstruction for patients in whom postmastectomy adjuvant radiation is rec-ommended. History of chest wall radiation is not a contraindication for an expander recon-struction. However, a higher complication rate may be seen with irradiated patients than nonirradiated patients [19].

Implant reconstruction may necessitate fur-ther surgery due to possible implant rupture. Therefore, a patient may instead elect recon-struction with an autologous tissue flap. There are several types of autologous tissue flaps. The latissimus dorsi reconstruction is an autol-ogous myocutaneous flap that involves trans-position of the skin, fat, a portion of the latissi-mus muscle, and blood vessels tunneled under the skin to the front of the chest. The abdomi-nal-based autologous flaps are the TRAM and DIEP flaps. The TRAM flap procedure uses abdominal skin, fat, blood vessels, and the rec-tus abdominis muscle. The two variants of the TRAM flap procedure include the pedicled flap and microsurgical free flap reconstruc-tions (Figs. 4A–4D). The pedicled TRAM is based on the superior epigastric vasculature and requires the full length of the rectus ab-dominis muscle [19]. The microsurgical tech-nique uses the inferior epigastric artery, and is generally preferred when improved vascular-ity of the flap is required [19].

The DIEP flap was introduced after the TRAM flap in an effort to reduce abdominal wall defects from donor-site morbidity, in-cluding abdominal hernia and weakening of the abdominal wall musculature [20, 21]. The DIEP free flap uses fat and skin from the ab-dominal wall but does not use the rectus mus-cle. The potential advantage of a DIEP flap may be less abdominal wall weakening al-though rectus abdominis function may still be compromised with DIEP because the pro-cedure necessitates microdissection of small

perforating vessels through the rectus mus-cle. However, the introduction of the DIEP flap was associated with a reduced number of myocutaneous perforators nourishing the flap, potentially leading to partial flap failure [21].

On thoracic CT, autologous flap recon-struction will show several findings. There is replacement of the normal glandular tissue of the breast with homogeneous fat attenuation. The atrophied rectus abdominis muscle [22] is visualized along the anterior chest wall with a TRAM reconstruction. Running parallel to the breast skin, a thin curvilinear line is often seen that represents the epithelial layer of the low-er abdominal tissue [19, 22]. The fat anterior to this line represents that of the native chest wall, whereas that deep in relation to it repre-sents abdominal wall fat [19] (Fig. 4A). Breast cancer can reoccur at the interface between the flap reconstruction and native tissue [23].

Free-flap autologous reconstruction has de-veloped to reduce donor site morbidity. CT angiography (CTA) of the chest, abdomen, and pelvis plays a significant role in presurgi-cal evaluation of vascular anatomy for poten-tial free-flap candidates. Presurgical delineation of vascular anatomy can help optimize surgi-cal planning, decrease time spent in the operat-ing room, decrease morbidity, and improve sur-gical outcome [24, 25]. Key anatomic variables to evaluate using CTA are vessel size, location relative to the umbilicus, course, and length. For example, a long or tortuous intramuscular course of a deep inferior epigastric perforator may ren-der it unfavorable for pedicle use [24]. CTA can

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Fig. 5—45-year-old perimenopausal woman who recently underwent left modified radical mastectomy for invasive ductal carcinoma and subsequently developed mass in left chest wall representing seroma.A, Contrast-enhanced chest CT image shows simple focal fluid collection (5 HU) overlying pectoralis muscles and extending laterally into left axilla (arrow). There is no gas, peripheral enhancement, internal septation, or heterogeneity.B, Focused breast ultrasound image shows anechoic fluid collection with minimal posterior acoustic enhancement. Ultrasound-guided aspiration was performed for symptomatic relief and confirmed diagnosis of seroma.

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Fig. 6—64-year-old woman with history of breast cancer who was treated with left modified radical mastectomy, adjuvant hormone therapy, and left chest wall radiation who presented with persistent pain due to hematoma.A and B, Contrast-enhanced chest CT images show rim-enhancing 25-HU focal fluid collection (arrows) in left mastectomy bed extending to axilla. C, Fat-saturated T2-weighted image shows hyperintense heterogeneous fluid collection. Although not seen in this image, hematocrit level may also be seen with hematomas.D, Unenhanced fat-saturated T1-weighted image shows that fluid collection has high T1 signal intensity, suggestive of hematoma.E and F, Contrast-enhanced fat-saturated T1-weighted image (E) shows no evidence of internal enhancement of fluid collection, which is confirmed on subtraction image (F).

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also be used in the evaluation of the gluteal arter-ies for potential free-flap transfer if the abdomi-nal wall is a suboptimal donor site. Postoperative CTA can be used to evaluate for anastomotic pa-tency or stenosis (Figs. 4E and 4F).

A final component of breast cancer surgical treatment is surgical staging of the axilla via sentinel lymph node biopsy or axillary dissec-tion. Surgical staging of the axilla is the stan-dard of care in the treatment of invasive breast carcinoma. It is less commonly performed for the noninvasive diagnosis of DCIS because of the lower incidence of lymph node involve-ment [2]. However, up to 20% of DCIS diag-nosed at core biopsy may be upgraded to in-vasive carcinoma at surgical excision. A study by Yen et al. [26] found that 10% of selected DCIS patients who underwent sentinel lymph node biopsy were found to have a positive sen-tinel lymph node [26]. However, the only indi-cator of a positive sentinel lymph node in that study was when the DCIS diagnosis arose from biopsy of a palpable mass. The routine use of sentinel lymph node biopsy for initial diag-

nosis of DCIS may not be supported. Sentinel lymph node biopsy may be considered on the basis of the extent of calcifications, presence of associated mass, or histologic grade. Sen-tinel lymph node biopsy is more commonly performed for DCIS treated with mastectomy because the presence of invasive or microinva-sive disease at final pathology would preclude sentinel lymph node biopsy after mastectomy.

Postsurgical ComplicationsMost wound complications related to breast

cancer surgery are relatively minor, self-limit-ed, and managed on an outpatient basis. The most common complication after breast can-cer surgery is seroma [27]. Additional postsur-gical complications include wound infection, hematoma, and chronic incisional pain.

SeromaA seroma is a serous fluid collection that may

develop in the postsurgical space after breast cancer surgery. The rich lymphatic drainage patterns of the breast [28], potential space creat-

ed by surgical excision, and low fibrinogen lev-els [29] within lymph fluid are thought to con-tribute to seroma formation. Seromas can form after lumpectomy, mastectomy or axillary sur-gery with variable frequency. They have been described as being more common in older and obese patients [30]. MRM is more frequently associated with seroma formation than lumpec-tomy [27–31]. Postsurgical seroma after MRM occurs in 20–50% of patients compared with 9–20% of patients after lumpectomy [27–32]. The use of electrocautery is associated with in-creased incidence of seroma formation [27, 28]. Although usually self-limited and not a serious postoperative complication, a seroma can im-pair healing and increase patient discomfort, particularly in mastectomy patients.

Surgical drains are routinely placed after mastectomy to prevent and evacuate a potential postoperative seroma. However, there is a lack of definite data regarding the length of time a drain should remain in place [33]. Drains are removed when the drain output has dimin-ished and as the skin flaps heal and adhere to the chest wall. Treatment of a seroma is depen-dent on the clinical situation. If asymptomatic, seromas are often left untreated in lumpectomy patients. If treatment is indicated, seromas can be managed with percutaneous aspiration [29] and pressure. Postoperative seromas do not necessarily delay adjuvant treatment. On chest CT, a seroma appears as a low-attenuation flu-id collection without internal enhancement lo-cated in the postsurgical breast, chest wall, or axilla (Fig. 5A). On ultrasound, it can vary in appearance from an anechoic fluid collection (Fig. 5B) to a complex fluid collection with heterogeneous echogenicity.

HematomaA hematoma is a less common postsurgi-

cal complication, with a reported incidence of 2–10% of breast cancer surgery cases [28]. Hematoma is thought to originate from uncau-terized vessels [28]. The size and clinical pre-sentation can be variable, with smaller volume hematomas sometimes presenting clinically as skin ecchymosis, whereas larger hematomas can be painful and necessitate surgical evacu-ation [28]. Patients who consume aspirin; non-steroidal antiinflammatory drugs; or certain over-the-counter supplements, such as fish oil [34], may be at higher risk for hematoma for-mation as are patients with known bleeding di-atheses. Small hematomas carry low morbid-ity and usually require no treatment. However, large or rapidly developing hematomas may necessitate surgical evacuation [28].

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Fig. 7—60-year-old woman with history of left breast invasive ductal carcinoma treated with modified radical mastectomy and pedicle transverse rectus abdominis muscle (TRAM) reconstruction who has now developed fat necrosis within TRAM.A, Unenhanced axial chest CT image shows left modified radical mastectomy and pedicle TRAM flap reconstruction, with coarse calcifications (arrow) in TRAM flap representing fat necrosis.B, Mediolateral oblique left mammogram shows fat density of TRAM with coarse calcifications (arrow) of fat necrosis.

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On CT, a postsurgical hematoma may have a variable appearance depending on its age. It usually appears as a low-attenuation mass in the breast, chest wall, or axilla (Figs. 6A and 6B) that may measure higher attenuation than a serous fluid collection early after it forms but may measure simple fluid attenuation as it breaks down, making it difficult to distin-guish from a seroma. On MRI, hematomas show variable signal intensity on T1-weight-ed and T2-weighted sequences depending on blood product evolution. Postoperative he-matomas may show a low-signal-intensity rim of hemosiderin on the T2-weighted se-quence (Fig. 6C), high signal intensity in the

fluid collection on the unenhanced T1-weight-ed sequence (Fig. 6D), and a fluid-fluid layer (hematocrit level). There should be no solid-tissue component or internal enhancement in a postoperative hematoma (Figs. 6E and 6F).

InfectionPostoperative infection manifesting as cel-

lulitis or abscess is another potential compli-cation of breast surgery. The rate of postoper-ative infection is variable, ranging from 1% to 20% [28]. No consistent correlation between the risk of infection and the type of breast can-cer surgery has been identified [28]. Diabetes, obesity, older age (> 65 years) [35], and nico-

tine use [36] are associated with an increased risk of postoperative infection. Staphylococcal organisms are the most common organism in postoperative breast infections. The presence of a large seroma increases the likelihood of associated postoperative infection [37], which may be explained by lymph stasis or per-cutaneous aspiration (during which skin bac-teria may be introduced into the seroma). Most episodes of cellulitis occur within 1 month of surgery. Delayed cellulitis is infrequent and may be related to lymph stasis [38].

On CT, cellulitis can appear as diffuse lin-ear soft-tissue strands in the adjacent subcuta-neous fat, often referred to as “soft-tissue fat

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FFig. 8—42-year-old woman with history of right breast cancer and bilateral modified radical mastectomies with implant reconstruction that included autologous fat grafting cranial to implants.A, Axial unenhanced CT image shows soft-tissue mass with central fat attenuation (arrow) and adjacent fat stranding in left anterior chest wall above level of implant. Area of established fat necrosis in right chest wall (arrowhead) shows no increased FDG uptake.B, Surveillance PET scan shows corresponding 18F-FDG-avid lesion (arrow).C and D, To further evaluate for possibility of breast cancer recurrence, contrast-enhanced breast MRI was performed. Axial T1-weighted (C) and fat-suppressed T2-weighted (D) images show fat signal in anterior left chest wall at site of FDG-avid lesion.E, Contrast-enhanced T1-weighted fat-suppressed image shows lesion enhances and shows suggestion of central fat (arrow). Of note, there are fat-containing lesions at same level in right chest wall that do not show enhancement (arrowhead) and are also consistent with fat necrosis.F, Ultrasound image of left chest wall shows two hypoechoic masses with suggestion of internal debris. Ultrasound-guided core biopsy of larger mass was performed. Pathology was consistent with fat necrosis.

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stranding.” The ultrasound appearance of cel-lulitis may appear as edema with linear hypo- or anechoic fluid interdigitated between fat lob-ules of the breast. Skin thickening, defined as greater than 3 mm is often seen. However, these imaging findings may not be dissimilar to the normal postoperative appearance of breast tis-sue after surgery, emphasizing the importance of clinical correlation. Mild incisional celluli-tis can be treated with oral antibiotics, but ex-tensive soft tissue infection requires IV therapy.

A postsurgical infection may be complicat-ed by abscess formation, usually within 1 to 2 weeks after surgery, presenting as a fluctuant tender mass at the surgical site. On CT, an ab-

scess appears as a low-attenuation fluid collec-tion with a thick or irregular enhancing wall. Ultrasound evaluation is usually performed as the first imaging test at the site of concern and may show a complex hypoechoic or isoechoic fluid collection. Mobile debris within the fluid collection and hypervascularity of the adjacent breast tissue may also be seen. Definitive ab-scess management usually requires surgical or percutaneous drainage depending on the size and clinical scenario.

Fat NecrosisFat necrosis can occur in a reconstructed

autologous flap due to an inadequate blood

supply to the flap (Fig. 7), in the reconstruct-ed breast of patients who have had autologous fat grafting performed to improve breast con-tour and symmetry [39] (Fig. 8), and at the site of breast conservation surgery (Fig. 9). Fat necrosis is a sterile inflammation of fat in the breast resulting from loss of vascular supply. Lipolysis, inflammatory cell infiltra-tion, and hemorrhage occur acutely followed by the formation of fibrous scar or a calcified cystic mass as the lesion evolves [40], result-ing in a variable imaging appearance.

Mammographically, fat necrosis can mani-fest as a spiculated or irregular mass, micro-calcifications, coarse calcifications, or lucent

A B C

D E

Fig. 9—73-year-old woman with history of left breast cancer after lumpectomy and radiation 2 years prior. Patient presented with new pain on lumpectomy scar.A and B, Craniocaudal (A) and mediolateral oblique (B) mammograms show benign posttreatment change. Radiopaque circles are mole markers.C, Recent surveillance PET scan shows soft-tissue mass at lumpectomy bed with increased associated 18F-FDG avidity.D and E, Nonfat-saturated T1-weighted images show postsurgical scar in lumpectomy bed. Note hypointense susceptibility from surgical clips (arrow, D). Anteriorly, there are two hypointense lesions (arrowhead, D) that show peripheral enhancement. Surgical biopsy was performed and found fat necrosis. Fat necrosis can have signal isointense to fat, often best seen on nonfat-saturated unenhanced T1-weighted images. However, fat necrosis can also show hypointense signal intensity on nonfat-saturated unenhanced T1-weighted images because of hemosiderin deposition.

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oil cysts. On ultrasound, fat necrosis may ap-pear as a complex mass or an anechoic round mass with thin hyperechoic walls; in the latter, posterior acoustic shadowing may distinguish fat necrosis from a simple cyst, which would have through transmission. On MRI, central bright signal intensity is seen on the nonfat-saturated T1-weighted sequence. However, if hemosiderin is present, it can result in low signal intensity on T1-weighted images. On the fat-suppressed T2-weighted sequence, hy-pointense signal intensity that follows fat sig-nal may be seen centrally [41]. To forgo biop-sy, the presence of central fat signal intensity (best seen on T1-weighted sequences) is the key to differentiating fat necrosis from tumor recurrence [19]. On the contrast-enhanced dy-namic sequence, fat necrosis may manifest as a mass with rim enhancement or variable non-masslike enhancement. On CT, the lesion will have fat attenuation centrally (Fig. 8A), and there may be adjacent soft-tissue fat stranding and enhancement. On PET, fat necrosis can have increased 18F-FDG uptake [42] (Fig. 8B) in an acute stage and therefore mimic disease recurrence. Correlation with CT or MRI with the patient’s history may assist with the diag-nosis of fat necrosis. The imaging appearance of fat necrosis on all imaging modalities can be indistinguishable from malignancy, some-times necessitating biopsy.

Flap NecrosisFlap necrosis is a problematic complica-

tion that may occur in TRAM flaps, latissimus dorsi autologous flaps, or skin flaps because of inadequate blood supply to a portion of the flap, with a reported incidence of 19.5% [43]. Obesity, previous breast or mediastinal radia-tion, and diabetes place patients at increased risk of developing flap necrosis [44]. There is a higher frequency of flap necrosis in TRAM flaps than latissimus dorsi flaps because of de-creased vascularization [43]. Necrosis of skin flaps occurs after SSM with a reported inci-dence of 24.3% [45]. Necrosis may range in severity from mild epidermolysis to severe infarction. Flap necrosis is a clinical diagno-sis, for which there is little role for imaging. Treatment ranges from conservative manage-ment (observation) to surgical débridement, depending on the severity of the necrosis.

LymphedemaSwelling of the extremity secondary to

lymphedema is a common late complication after axillary surgical staging of breast can-cer. It occurs with a higher frequency after axillary lymph node dissection than sentinel

lymph node biopsy. Lymphedema affects 10–20% of women after breast cancer treatment [46]. Signs and symptoms include arm edema; skin thickening; and heaviness of the chest, breast, and arm. Lymphedema is a clinical di-agnosis, with little indication for imaging. On cross-sectional imaging, lymphedema appears as asymmetric size of the affected arm, trabec-ular thickening and soft-tissue fat stranding of the breast and upper extremity, and skin thick-ening. Surgical clips in the axilla together with these findings should suggest this diagnosis.

ConclusionBreast cancer patients frequently undergo

cross-sectional imaging during or after treat-ment or surveillance or in the evaluation of acute symptoms. Thoracic CT examinations often show findings related to surgical treat-ment. Postsurgical changes visible on thorac-ic CT are variable and dependent on the type of surgical treatment. Expected postsurgical complications may also be seen on thoracic CT, including fluid collection, infection, fat necrosis, and lymphedema. Recognition of the posttherapeutic manifestations of breast cancer is important to avoid unnecessary workup and minimize patient anxiety.

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