Spindle cell haemangioendothelioma: a clinicopathological and immunohistochemical study indicative of a non‐neoplastic lesion

Spindle cell haemangioendothelioma is an uncommon vascular lesion, of which 35 cases have been previously reported. A further 20 cases are reported herein. These lesions affected a wide age range in both sexes, and showed a predilection for the extremities. Twelve patients had multiple lesions and, in these cases, local progression over many years but no true recurrence was typical. None of the 20 patients developed metastases, but one later developed an angiosarcoma. Individual cases were associated with congenital lymphoedema. Klippel-Trenaunay syndrome and early-onset varicose veins. Histologically, in addition to the admixture of cavernous spaces and solid spindle cell/epithelioid cell areas, the presence both of irregularly distributed and perivascular smooth muscle cells and of malformed variably-sized vessels at the periphery of almost every lesion was noted in each case. Reticulin staining, immunohistochemistry and electronmicroscopy revealed the presence of primitive vessel formation and partial endothelial differentiation in the solid spindle cell areas. Combining these data with those from previously published series, it is suggested that spindle cell haemangioendothelioma is a non-neoplastic lesion (rather than a borderline malignancy as it is currently regarded) and that its development correlates with histological and/or clinical evidence of a malformed vasculature at the affected site.