Fine needle aspiration (FNA) appearances of malignant myoepithelioma of the parotid gland

Abstract

We describe the FNA features of five cases of malignant parotid myoepithelioma, the majority of which were thought clinically to be recurrent pleomorphic adenomas. A major finding was cell shape variation: round-oval, polygonal or spindle-shaped, with basophilic cytoplasm. Many were epithelial and plasmacytoid-like and had nuclear grooves, pseudoinclusions, and multinucleation. The true myoepithelial nature of the neoplastic cells was identified in all cases, but only two showed obvious cytological malignant features, both initially and on re-examination. FNA of malignant myoepithelioma may thus show overt features of malignancy, or may lack atypia and malignancy can only be identified on histology. The correct diagnosis can be predicted in FNA samples in certain cases, both in terms of typing and malignancy, whilst sometimes only the myoepithelial nature of the lesion can be assessed.

Myoepithelioma of the Parotid Gland Initially Diagnosed by Fine Needle Aspiration Cytology and Immunocytochemistry

“…It had, in addition, intranuclear cytoplasmic inclusions, an important characteristic of papillary thyroid carcinoma that has been observed in other thyroid and extrathyroidal neoplasms, including pleomorphic adenoma 16,17 and malignant plasmacytoid myoepithelioma. 18,19 Stellate cells having cytoplasmic processes, as observed in our case, were also seen in the plasmacytoid myoepithelioma case described by Orell et al 15 Similar processes with myofibrillike bundles of actin and myosin filaments are characteristic of normal, nonneoplastic myoepithelial cells, which embrace the acini of the glands. Their contraction, induced by the nervous system and hormones, serves to expel the secretions of breast and apocrine sweat glands.…”

Myoepithelioma of the Parotid Gland – Diagnosis and Surgical Treatment Difficulties: a Case Study

“…Vast infiltration in the case of malignant myoepithelioma enforces a bad diagnosis [10,[21][22][23]. Differentiation between benign and malignant epithelioma is difficult despite accurate diagnostic features.…”

Letters to the Editors

“…Myoepithelial cells assume different morphologic forms, such as spindle, stellate, plasmacytoid and epithelioid, 5,9 of which the spindle cell type is the most common, accounting for almost 70% of myoepitheliomas. 4 These cells have some very specific functional abilities that are important for the growth pattern of some salivary gland tumors, like adenoid cystic carcinoma, pleomorphic adenoma and salivary duct carcinoma.…”

“…[6][7][8][9] AP is noted in the mucin pools of colloid carcinoma and, when seen, is distinctive enough to suggest the diagnosis.…”