Cytologic findings and potential pitfalls in proliferative myositis and myositis ossificans diagnosed by fine needle aspiration cytology: report of four cases and review of the literature.

Proliferative myositis (PM) and myositis ossificans (MO) are two uncommon, benign pseudosarcomatous lesions of soft tissue. Despite their benign nature, they are often misdiagnosed for malignant soft tissue tumors because of their alarming clinical presentation. Fine needle aspiration cytology (FNAC) is a quick and simple method that can accurately diagnose such lesions, provided that the cytopathologist is adequately familiar with the cytomorphological features of these lesions as opposed to the features of sarcomas. In this report, we present three cases of PM and one case of MO diagnosed by FNAC. Their cytomorphological features are described, and related literature is reviewed.