Intravascular papillary endothelial hyperplasia (Masson's tumor) is a reactive vascular lesion of obscure etiopathogenesis, often seen in the head and neck. Its presentation as a scalp swelling, however, is extremely uncommon. We describe the first report in an adult, being treated for bipolar illness. A young male presented with a right frontotemporal scalp swelling since 3 weeks. He was also being treated for bipolar illness with olanzapine. Examination revealed a soft, non-pulsatile swelling. After inconclusive aspiration results, a complete excision was performed. Histopathology revealed proliferating endothelial cells arranged as papillary fronds confined to vessel lumina, devoid of atypia, accompanied by thrombosed vessels facilitating a diagnosis of Masson's tumor. The patient is free of recurrence five months after surgery. Further studies on a possible effect of olanzapine on vascular proliferation in experimental in vivo and in vitro models would definitely aid in elucidating clinical relevance, if any.
Keywords: CD34 antigen; endothelial; olanzapine; scalp; vascular.