Alveolar rhabdomyosarcoma is a rare sarcoma and is less common in adults than in children. However when it occurs in adults the head and neck region is the second most common site of origin.
The key cytological finding is the so-called “floret cell” a multinucleated cells as seen in the figures, otherwise the smaller cells are frequently mistaken for lymphocytes or small cell carcinoma. Cell block with monoclonal antibody staining by immunoperoxidase methodology is critical since frequently this diagnosis is not commonly thought of. This case was negative for cytokeratin and leukocyte common antigen but positive for vimentin and desmin. Alveolar rhabdomysarcomas may have genetic changes of T(2;13)(q35;q14) translocations and 70-85% express PAX3-FKHR or PAX7-FKHR fusion transcripts. Thus repeat sampling for submission to cytogenetics or for FISH technique testing can be confirmatory. Prognosis is poor.
Chen KTK, Rhabdomyosarcoma in an adult presenting with nodal metastasis: A pitfall in fine-needle aspiration cytology of lymph nodes. Diagn Cytopathol 2005;32:303-306.
This case is contributed by Dr. Larry Fowler from the Department of Pathology, University of Texas Health Science Center at San Antonio.