Fine needle aspiration of poorly differentiated rhabdomyosarcoma presenting with quadriparesis. A case report

The diagnosis of metastatic poorly differentiated rhabdomyosarcoma (RMS) in lymph node specimens by fine needle aspiration presents a difficult problem since it is virtually indistinguishable from other small round cell neoplasms.

Fine needle aspiration was performed under radiologic guidance on an extradural, space-occupying lesion of unknown etiology in the region of the C-6 and C-7 vertebrae in a 20-year-old male who was hospitalized with quadriparesis. Cytologic examination suggested a metastatic tumor consistent with the diagnosis of rhabdomyosarcoma. A subsequent search for the primary tumor site revealed a soft tissue swelling in the right calf muscle. Light microscopic, ultrastructural and immunocytochemical examination of multiple Tru-cut biopsy specimens from the swelling in the right calf muscle confirmed the diagnosis of poorly differentiated embryonal rhabdomyosarcoma.

Immunostaining is useful for muscle proteins in the detection of poorly differentiated forms of embryonal rhabdomyosarcoma. Electron microscopy is of limited use in such cases.