Solid dendritic cell angiosarcoma: re-interpretation of extraskeletal sarcoma resembling Ewing's sarcoma.

Twenty cases of a type of extraskeletal tumour resembling Ewing's sarcoma (Angervall and Enzinger, 1975) were studied. The tumour affected mainly soft tissues in a variety of sites. Throughout the long follow-up period, there was only one instance of non-recurrence after excision. Most of the tumours became generalised within 3 years. One case developed general spread after 13 years. The tumour shows predominantly expansive growth and a solid architecture which, in places changes to reticular or sinusoidal structures. The predominant dendritic tumour cells show multiple junction complexes. Weibel-Palade granules can occasionally be demonstrated in their cytoplasm. In foci of peritheliomatous pattern the tumour cells become elongated, contain an abundance of endoplasmic reticulum and give rise to pericellular basement membranes, although typical collagen was rarely found. Judged by its structural and cytological features the tumour is a form of angiosarcoma, mostly of the endothelial type but with pericytic variations. Since neither its cellular features nor its biological behaviour correspond to those of Ewing's sarcoma, a change of name is proposed.