Sclerosing, pseudovascular rhabdomyosarcoma in adults. Clinicopathological and immunohistochemical analysis of three cases.

Rhabdomyosarcoma in adults represents a rare soft tissue neoplasm which is seen most frequently in its pleomorphic subtype in this age group. Very rarely, clear cell and spindle-cell variants have been reported. In this study we describe three cases of rhabdomyosarcoma in adult patients, characterised by prominent hyaline sclerosis and a pseudovascular growth pattern. All cases were identified in the consultation files of one of the authors and routinely processed. Immunohistochemical studies were performed on paraffin sections with the alkaline phosphatase-antialkaline phosphatase method. The patients, two women and one man, were 40, 41, and 56 years old. One developed a deep-seated soft tissue mass in the left lower leg, and one, a tumour of the left upper jaw. In one patient a bone tumour in the proximal body of the sacrum without extension into soft tissues was seen. The patients were treated by wide excision, piecemeal excision and incomplete excision in one case each; additional radiotherapy was performed in all three cases, and chemotherapy in two patients. In one patient multiple pulmonary metastases were noted, which showed progression despite systemic chemotherapy. Histologically, the neoplasms were composed of round/polygonal and spindle-shaped tumour cells including typical rhabdomyoblasts. In all cases a pseudovascular pattern and prominent hyaline sclerosis of the intercellular matrix was seen. Immunohistochemically, tumour cells stained positively for desmin and muscle actin (HHF35) and also for markers of striated muscle differentiation (myogenin, MyoD1, fast myosin). In this paper an unusual morphological variant of rhabdomyosarcoma arising in adult patients is described, which should be added to the morphological spectrum of these neoplasms.