PRIMARY RHABDOMYOSARCOMA OF THE ILIAC BONE IN AN ADULT - A CASE MIMICKING FIBROSARCOMA

Primary rhabdomyosarcoma of bone is exceedingly rare. We present a cas e of rhabdomyosarcoma of the iliac bone in a 32-year-old male. Histolo gically, the tumour consisted mainly of a uniform proliferation of elo ngated spindle cells arranged in a herring bone pattern, simulating fi brosarcoma. Focally there was a conventional embryonal pattern with sc attered rhabdomyoblasts possessing an eosinophilic cytoplasm. Immunohi stochemical studies disclosed expression of muscle markers such as des min and muscle-specific actin, in both the embryonal and spindle-cell areas and myoglobin only in the embryonal areas. Such histological fea tures are unusual for classical embryonal rhabdomyosarcoma. The anatom ical site and age of the patient are also atypical.