Sinusoidal hemangioma. A distinctive benign vascular neoplasm within the group of cavernous hemangiomas.

Twelve cases of sinusoidal hemangioma, a distinctive subset of the group of lesions known as cavernous hemangioma, are described. All presented as solitary subcutaneous/deep dermal lesions in adults, predominantly females. Five arose on a limb and five on the trunk; two of the latter were situated in mammary subcutaneous tissue. Histologically they were characterized by dilated, interconnecting, thin-walled vascular channels that frequently showed a pseudopapillary pattern. These vessels had a predominantly lobular architecture but peripherally showed focally ill-defined spread into subcutaneous tissue. The lining endothelium was single-layered but showed focal pleomorphism and hyperchromasia, which, combined with the pseudopapillae and apparent infiltrative pattern in areas, raised the possibility of angiosarcoma in four cases, most notably in the breast lesions. This possibility was further suggested by the presence of pseudonecrotic central infarction in two cases. Follow-up in eight cases, however, has revealed no tendency for either local recurrence or metastasis.