Pitfalls in the diagnosis of adult rhabdomyoma by fine needle aspiration: report of a case and a brief literature review.

Fine needle aspiration (FNA) is a valuable, noninvasive, commonly used technique in the diagnoses of head and neck tumors. Adult rhabdomyoma is a rare benign tumor of striate muscle tissue usually located in the head and neck region. Cytomorphologically, the tumor cells have eosinophilic finely granular cytoplasm, which sometimes can mimic other tumors. We report a case of adult rhabdomyoma, which was initially misinterpreted as granular cell tumor on FNA biopsy due to lacking of typical cytological features of adult rhabdomyoma. We recommend that adult rhabdomyoma should be included in differential diagnoses when the cytological features are suggestive of granular cell tumor. A panel of immunohistochemical stains including S100, desmin, and myoglobulin may also be helpful in making correct diagnosis.