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Case 100 Answer


Low grade minor salivary gland neoplasm. Definite classification requires complete resection of the tumor to evaluate better architecture and interphase with adjacent tissues. 



Smears were not contributory. Biopsy shows only minute fragments of tissue with solid proliferation of  bland and uniform low grade cells without obivous ducts or evidence of nuclear pleomorphism, prominent nucleoli, necrosis or mitotic activity. 

Immunostains were requested in an attempt to further classify. The neoplastic cells stain very strong  with CK7 and CK19. p63 stains peripheral cells suggestive of a myopithelial cell pattern around ducts .  The following immunostains are negative: SMA, calponin, CEA, CK20, p53 and S100. 

The morphology and staining pattern is consistent with a low grade salivary gland neoplasm. Differential diagnosis includes a cellular area of a pleomorphic adenoma (benign mixed tumor) vs Low Grade Mucoepidermoid Carcinoma or a Polymporphic Low Grade Adenocarcinoma. Based in cytology, in abscence of myxocondroid stroma and fibrillary or metachromatic background, I can not make a definitive dx of a pleomoprhic adenoma. Solid proliferation of intermediate cell in low grade mucoepidermoid Ca are sometimes similar in appearance to the cellular zones of modified myoepithelial cells in pleomorphic adenomas. 

Although the tumor is focally positive for CD117 in patchy distribution, the tipical cribiform histology with dual population  of epithelial and myoepithelial cells is not present,  arguing against the possibility of Adenoid Cystic Ca. The possibility of acinic cell Ca is also low in intraoral cavity. I do not see the typical poligonal morphology with granular basophilic cytoplasm typical of Acinic Cell Ca.