[Target-like hemosiderotic hemangioma. Further differential diagnosis of Kaposi sarcoma]

Targetoid haemosiderotic haemangioma (THH) can be differentiated from other angiomatous lesions by the characteristic findings on clinical and histological examination. Clinically the solitary lesion is suggestive of a melanocytic or angiomatous origin, surrounded by a haemorrhagic halo in the acute phase. Histological findings vary depending on the duration of the alteration. The pattern has a superficial and a deep dermal component. In the papillary body lesional capillaries are lined by prominent endothelial cells. The surrounding tissue is oedematous and contains masses of erythrocytes or haemosiderin and a lymphocytic infiltrate. Vessels in the deeper dermis have a lymphatic appearance and surround adnexal structures. Further possible similarities with Kaposi sarcoma are dissecting vascular lumina between collagen bundles and spindle cell areas. However, has no atypical cells, eosinophilic globules or apoptotic endothelial cells. Immunohistochemical investigations, which have now revealed BMA 120 for the first time in THH as well as factor VIII-R antigen and Ulex europaeus I lectin, have not so far made any substantial contribution to the differential diagnosis and histogenesis of THH, because markers distinguishing lymphatic from vascular endothelia are still lacking.