[448] Myoepithelial Carcinoma of the Salivary Glands: Cytomorphologic Characteristics and Differential Diagnosis

SL Nugent, MP Tilson, SZ Ali. The Johns Hopkins Hospital, Baltimore, MD

Background: Myoepithelial carcinomas (MC) are extremely uncommon accounting for < 0.1% of all primary salivary gland neoplasms. Cytomorphologic descriptions of MC are rare, mostly limited by case reports. The current study from a single large institution elaborates on morphologic criteria and differential diagnoses of MCs.
Design: A retrospective search of the cytopathology archives from a large tertiary care center for a 19-year period (1989-2008) revealed ten cases of MCs in eight patients (primary-9, metastatic-1). Material was obtained by fine needle aspiration (FNA) performed with or without radiologic guidance. Smears were stained with Diff Quik and Papanicolaou stains. Clinical outcome and histopathologic follow-up was additionally reviewed and correlated.
Results: There were two males and six females (M: F, 1:3), ranging in age from 34-87 years (mean age 63.6 yrs). The anatomic locations were; parotid (5), submandibular (2), parapharyngeal (2), lung (1). The most common clinical presentation was an incidental mass or facial pain. The tumor size ranged from 1.5-3.5 cm (mean size 2 cm). The initial FNA diagnoses were: salivary gland neoplasm, NOS (4), epithelial neoplasm, NOS (3), pleomorphic adenoma [PA] (3). The histologic diagnoses were; MC (8) and high-grade MC (2). Cytomorphologic characteristics were; hypercellular smears, predominantly discohesive single cells, syncytial or papillary-like fragments with perivascular nesting, rare/focal metachromatic stroma, plasmacytoid to epithelioid cells with cytoplasmic tails, oval to spindled/fusiform nuclei, cells with clear/vacuolated cytoplasm and abundant naked nuclei. A key feature was cellular monotony with only slight anisonucleosis. Cases with high-grade MC follow-up disclosed mitoses and karryorhexis. Immunostaining was done in seven cases using S100 protein, epithelial and smooth muscle markers and displayed expected results. Clinical outcome was available in all cases-alive without disease (8).
Conclusions: FNA interpretation of MC is extremely difficult due to its rarity and highly variegated cytomorphologic appearance leading to a more generic cytologic diagnosis of “salivary gland neoplasm, NOS”. Cellular monotony with mostly discohesive cells or papillary-like phenotype in a stroma-poor lesion should raise the possibility of an MC. Immunostaining can be helpful in selected cases. Differential diagnosis includes PA, myopeithelioma, and metastatic melanoma.
Category: Cytopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 53, Wednesday Afternoon

 

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