Most Nonparotid “Acinic Cell Carcinomas” Represent Mammary Analog Secretory Carcinomas

Abstract

Acinic cell carcinoma (ACC) is a low grade salivary gland malignancy characterized by serous acinar differentiation. Most ACCs arise in the parotid gland, but ACCs have been reported to originate in non-parotid salivary glands where where serous acini are less abundant. Given the recent discovery of mammary analogue secretory carcinoma (MASC) – a salivary malignancy that histologically mimics ACC – a retrospective re-evaluation of non-parotid ACCs is warranted. The surgical pathology archives of The Johns Hopkins Hospital were searched for all ACCs arising outside of the parotid gland. For each case, the histologic slides were reviewed; immunohistochemistry (mammaglobin, S100 protein) was performed; and confirmatory ETV6 break-apart FISH assay was completed. Demographic and clinical data was obtained from the medical records. Fourteen extra-parotid tumors diagnosed as ACC were identified. Eleven of 14 (79%) tumors harbored the ETV6 translocation (oral cavity = 9 of 11; submandibular gland = 2 of 2). The translocation positive tumors occurred in 7 women and 4 men ranging in age from 20–86 years (mean, 56), and usually presented as painless masses. Immunohistochemistry for mammaglobin and S100 was positive in all 11 translocation positive tumors, but negative in the 3 translocation negative tumors. Histologically, the translocation positive tumors exhibited uniform cells with vacuolated cytoplasm, microcystic/cystic and papillary architecture, and intraluminal secretions; but the presence of basophilic cytoplasmic granules was conspicuously absent. Basophilic cytoplasmic granules, indicative of true serous acinar differentiation, were present in the 3 translocation negative tumors. Of the translocation positive tumors, only one locally recurred, and none metastasized. Most alleged ACCs of non-parotid origin actually represent misclassified MASCs. The impact of diagnostic error is mitigated by the low grade nature of MASC that, like ACCs, do not appear to be clinically aggressive.

Searching for mammary analog secretory carcinoma of salivary gland among its mimics

“…A recent study has suggested that 'acinic cell carcinomas' that occur outside of the parotid are actually mammary analog secretory carcinomas. 15 A higher incidence of nodal metastasis and poorer disease-free survival seem to occur when compared with acinic cell carcinoma. 3,4 Figure 3 Adenocarcinoma, NOS.…”

Morphology in Conjunction with Immunohistochemistry is Sufficient for the Diagnosis of Mammary Analogue Secretory Carcinoma

“…The majority of MASCs typically demonstrate coexpression of S100 protein and mammaglobin, although focal weak or absent expression of S100 protein has been reported in intraoral tumors [1,[22][23][24]. Using the above histologic features as a springboard for diagnosis as well as supporting coexpression of S100 protein and mammaglobin, we rendered a diagnosis of MASC in total of 19 consultation cases sourced from the University of Virginia and the Mount Sinai Health System-Beth Israel Medical Center.…”

“…In our experience the histologic and cytologic features of adenoid cystic carcinoma allow its easy distinction from MASC; although, in cases with high-grade transformation molecular studies would be prudent. Recently, MASC have been described in the oral cavity [22,24]. Given the predilection of polymorphous low-grade adenocarcinoma (PLGA) for this site, this tumor may enter the differential diagnosis.…”

“…Both share cytologic monotony and variable architectural patterns as well as the potential for co-expression of S100 protein and mammaglobin. However, the degree of secretions and cytoplasmic [22,24]. These two intraoral tumors also demonstrated isolated tumor cells with nuclear p63 expression [22].…”

Update from the 4th Edition of the World Health Organization Classification of Head and Neck Tumours: Tumors of the Salivary Gland

“…Secretory carcinoma differs from acinic cell carcinoma epidemiologically in that the sex predilection is more equal, and secretory carcinoma arise in minor salivary sites more frequently than acinic cell carcinoma [3,5]. Histologically, secretory carcinoma share nearly identical growth patterns to acinic cell carcinoma (Fig.…”