TARGETOID HEMOSIDEROTIC HEMANGIOMA - ANOT HER CONDITION TO BE INCLUDED IN THE DIFFERENTIAL-DIAGNOSIS OF KAPOSI-SARCOMA

Targetoid haemosiderotic haemangioma (THH) can be differentiated from other angiomatous lesions by the characteristic findings on clinical a nd histological examination. Clinically the solitary lesion is suggest ive of a melanocytic or angiomatous origin, surrounded by a haemorrhag ic halo in the acute phase. Histological findings vary depending on th e duration of the alteration. The pattern has a superficial and a deep dermal component. In the papillary body lesional capillaries are line d 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 Ka posi sarcoma are dissecting vascular lumina between collagen bundles a nd spindle cell areas. However, has no atypical cells, eosinophilic gl obules or apoptotic endothelial cells. Immunohistochemical investigati ons, 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 h istogenesis of THH, because markers distinguishing lymphatic from vasc ular endothelia are still lacking.