LETTER TO THE EDITOR

Differences on clinicopathologicalprofile from intraoral minorsalivary gland tumors aroundthe world

To the Editor:We read with great interest the paper from Wang

et al.1 regarding intraoral minor salivary gland tumors(IMSGT). This and our recently published article2 arethe largest clinicopathological studies on IMSGT re-cently reported in the literature; both are based on thelast updated World Health Organization classificationof salivary gland tumors.3 As many IMSGT are rela-tively uncommon lesions, large series are useful tocompare their incidence and sociodemographic andclinical features, and to evaluate differences in specificracial groups and geographic areas. When comparingthese 2 studies, one from North America and anotherfrom Asia, we could identify some important differ-ences. As both studies used similar diagnostic criteria,personal histological interpretation criteria would notjustify all differences, most of them probably represent-ing true racial, environmental, and geographical differ-ences.

The first point was the frequency of the IMSGThistological subtypes. Both studies reinforced that onminor salivary glands, benign and malignant tumorshave an almost equal frequency. Some studies havepreviously reported that pleomorphic adenoma (PA)seems to have a higher prevalence among Japanese.4

According to the data of Wang et al.,1 PA and myoep-ithelioma, sometimes interpreted as a spectrum of PA,represented together 44% of all tumors from a total of46% of benign tumors. In contrast, our findings re-vealed that PA represented 33% of all tumors from atotal of 56% of benign tumors.2 This could be ex-plained by the fact that cystadenomas and canalicularadenomas represented 11% and 9% of all tumors, re-spectively, in Pires et al.,2 in contrast to less than 1%and 0%, respectively, in Wang et al.1 This shouldindicate that cystadenomas and canalicular adenomasare more common in the North American than Japaneseand Chinese populations (Table I).

Malignant IMSGT revealed some different featuresin both studies as well. Mucoepidermoid carcinoma(MEC) and adenoid cystic carcinoma (ACC) repre-

sented the most common malignant tumors, but their

136

prevalence was different in the 2 studies. Studies fromJapan have reported a greater incidence of adenoidcystic carcinoma in comparison to mucoepidermoidcarcinoma,4 similar to the finding of Wang et al.,1 butin contrast to most papers from Europe and America.2

Polymorphous low-grade adenocarcinoma seems to berare in Japan,4 but represented 5% of all IMSGT in bothstudies.1,2 Other interesting findings were the higherfrequency of acinic cell adenocarcinoma in Pires et al.2

in contrast to the higher frequency of carcinoma, ex-pleomorphic adenoma, and myoepithelial carcinoma inWang et al.1 These findings together reinforce thatthere are also some differences in the frequency ofmalignant IMSGT when comparing the American andAsian populations (Table I).

Site distribution revealed that the palate, buccal mu-cosa, and upper lip were the common locations ofIMSGT in both studies. Palate, the buccal mucosa, thefloor of mouth, the tongue, and the alveolar mucosawere the common sites for malignant tumors. Salivarygland tumors were mostly benign on the upper lip butmalignant on the lower lip. It is interesting to note thatin almost all of the common benign and malignanttumors reported by Wang et al.,1 there was a markedpredilection for the palate, whereas this clear distribu-tion was not highlighted by the results of Pires et al.2

Table I. Comparison on the most common benign andmalignant minor salivary gland tumors from Pireset al.2 and Wang et al1

Pires et al. Wang et al.

Histological type n % n %

Benign 305 56 340 46Pleomorphic adenoma 181 33 278 37Canalicular adenoma 50 9 None NoneCystadenomas 58 11 6 �1Myoepithelioma 1 �1 49 7

Malignant 241 44 397 54Mucoepidermoid carcinoma 125 23 91 12Adenoid cystic carcinoma 35 6 143 19Polimorphous low-grade

adenocarcinoma28 5 34 5

Acinic cell adenocarcinoma 21 4 7 �1Adenocarcinoma NOS 21 4 41 6Carcinoma ex-pleomorphic

adenoma2 �1 22 3

Myoepithelial carcinoma 1 �1 24 3

NOS, not otherwise specified.

This could be even more evident when analyzing, for

OOOOEVolume 105, Number 2 Letter to the Editor 137

example, the site distribution of polymorphous low-grade adenocarcinoma and acinic cell adenocarcinomaon both studies (Table II).

Women were more often affected than men in thegreat majority of histological subtypes from the data ofPires et al.,2 except for adenocarcinoma not otherwisespecified (NOS). In contrast, malignant tumors weremore common in men in the study by Wang et al.,1

especially by the fact that adenocarcinoma NOS, car-cinoma ex-pleomorphic adenoma, and myoepithelialcarcinoma showed a marked prevalence for men. It isalso interesting to call attention to the marked predilec-tion for women of polymorphous low-grade adenocar-cinoma and acinic cell adenocarcinoma in Pires et al.2

and the predilection of cystadenomas for men in Wanget al.1 We also observed an interesting difference in themean age range for most histological subtypes in bothstudies. On average, the mean age of Chinese patients1

was in the fifth decade of life, whereas most NorthAmerican patients were diagnosed in their sixth toseventh decades of life.2 Retrospective studies usuallydo not permit evaluation of symptom intervals, as this

Table II. Comparison on site distribution on the mostfrom Pires et al.2 and Wang et al1*

P

Histological type P BM

BenignPleomorphic adenoma 40 18

MalignantMucoepidermoid carcinoma 34 14Adenoid cystic carcinoma 40 17Polimorphous low-grade adenocarcinoma 39 18Acinic cell adenocarcinoma 19 33Adenocarcinoma NOS 43 14

P, palate; BM, buccal mucosa; L, lips; FM/AM, floor of mouth/alveo*Numbers are expressed in %.

Table III. Comparison on gender and age distributiongland tumors from Pires et al.2 and Wang et al1

P

Histological type M, % F

Benign 38Pleomorphic adenoma 38Cystadenomas 43

Malignant 39Mucoepidermoid carcinoma 40Adenoid cystic carcinoma 49Polimorphous low-grade adenocarcinoma 18Acinic cell adenocarcinoma 19Adenocarcinoma NOS 57

NOS, not otherwise specified.

information is rarely reported on laboratory registries,

so it is difficult to interpret if the differences are due toearlier detection of the disease or reflect a true regionalvariation in age distribution (Table III).

In summary, IMSGT are a heterogeneous group oftumors and large series are important to understandtheir frequency and sociodemographic and clinicalindividual characteristics. Reports from differentpopulations using the same diagnostic criteria areessential to compare and estimate true racial andgeographical variations in these uncommon head andneck tumors.

Fábio Ramôa Pires, DDS, PhDOral Pathology

State University of Rio de JaneiroRio de Janeiro, Brazil

Oslei Paes de Almeida, DDS, PhDOral Pathology

Piracicaba Dental SchoolState University of Campinas

on benign and malignant minor salivary gland tumors

al. Wang et al.

L FM/AM P BM L FM/AM

9 3 77 10 10 �1

1 22 58 12 8 196 29 57 12 6 121 11 82 6 6 63 5 43 14 14 295 38 39 17 2 37

cosa; NOS, not otherwise specified.

e most common benign and malignant minor salivary

al. Wang et al.

Mean age, y M, % F, % Mean age, y

58 48 52 4151 48 52 4461 67 33 4662 54 46 4955 41 59 4359 46 54 5069 50 50 5258 43 57 5470 78 22 50

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ires et

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OOOOE138 Letter to the Editor February 2008

Gordon Pringle, DDS, PhDSow-Yeh Chen, DDS, PhD

Oral Pathology SectionDepartment of Pathology and Laboratory Medicine

Temple University School of MedicinePhiladelphia, Pennsylvania

REFERENCES1. Wang D, Li Y, He H, Liu L, Wu L, He Z. Intraoral minor salivary

gland tumors in a Chinese population: a retrospective study on 737cases. Oral Surg Oral Med Oral Pathol Oral Radiol Endod

2007;104:94-100.

2. Pires FR, Pringle GA, Almeida OP, Chen SY. Intra-oral minorsalivary gland tumors: a clinicopathological study of 546 cases.Oral Oncol 2007;43:463-70.

3. Barnes L, Eveson JW, Reichart P, Sidransky D. World HealthOrganization classification of tumours. Pathology and genetics—head and neck tumors. Lyon: IARC Press; 2005.

4. Toida M, Shimokawa K, Makita H, Kato K, Kobayashi A,Kusunoki Y, et al. Intraoral minor salivary gland tumors: a clin-icopathological study of 82 cases. Int J Oral Maxillofac Surg2005;34:528-32.

doi:10.1016/j.tripleo.2007.08.042