Introduction: Myoepithelial carcinoma (MECA) is an infrequently recognized salivary gland (SG) neoplasm that commonly develops within a preexisting pleomorphic adenoma (MECA ex PA). Fine-needle aspiration (FNA) biopsy reports of this neoplasm are largely restricted to small series and single case reports.
Methods: Our cytopathology files were searched for examples of SG MECA/MECA ex PA having confirmatory histopathologic verification. Conventional FNA biopsy smears were performed, and exfoliative specimens processed using standard techniques.
Results: Thirteen cases from 9 patients (M:F = 3.5:1; age range: 36 to 95 years, mean age = 60 years) met inclusion criteria. FNA biopsy sites included parotid gland (4), trunk (2), scalp (2), and neck (2). Exfoliative specimens included pleural fluid (1), bronchial brushing (1), and bronchoalveolar lavage (1). Most cases were metastatic deposits (8; 62%), 4 were primary neoplasms, and 1 a local recurrence. FNA diagnoses were MECA ex PA (6; 46%), myoepithelial neoplasm (2), PA (2), basaloid neoplasm (1), atypical myoepithelial cells (1), and myxoma (1). Ancillary testing in 2 cases showed positive staining for myoepithelial markers. Cytologic features were that of a low-grade neoplasm composed principally of epithelioid/polygonal cells exhibiting minimal if any cytologic atypia. Myxoid and chondromyxoid stroma was often the dominant feature in MECA ex PA aspirates.
Conclusion: In the primary setting, a cytologic diagnosis of MECA/MECA ex PA is extremely challenging if at all possible. Due to overwhelming amounts of stroma, the diagnosis may be challenging in some cases of metastatic MECA ex PA.
Keywords: Carcinoma ex pleomorphic adenoma; Fine needle aspiration biopsy; Milan system; Myoepithelial carcinoma; Salivary gland.
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