Solitary fibrous tumour arising at unusual sites: analysis of a series.

Solitary fibrous tumours ('pleural fibromas') are well-recognized in the pleura, but their rare occurrence at other sites has only become appreciated in recent years, as a consequence of which extrapleural examples often go unrecognized or misdiagnosed. Eight cases (three peritoneal, two retroperitoneal, two intrapulmonary and one mediastinal) are presented herein. All but one presented in adulthood, and three were asymptomatic chance findings. Size ranged from 0.8 to 26 cm in maximum diameter. To date, none has behaved in an aggressive fashion. Histologically, these lesions are entirely comparable to their pleural counterparts, and accurate diagnosis is largely dependent on appreciation of their potential extrapleural location. Immunohistochemistry in seven cases favoured myofibroblastic/fibroblastic differentiation, in keeping with the putative submesothelial origin of these lesions.