D2-40 highlights lymphatic vessel proliferation of angiolymphoid hyperplasia with eosinophilia.

Angiolymphoid hyperplasia with eosinophilia (ALHE) is a benign, uncommon idiopathic condition, characterized by cutaneous papules or nodules, whose etiopathogenesis is still unclear. It has been considered an angioproliferating lesion (epithelioid hemangioma) since histologically it is marked by a proliferation of blood vessels, accompanied by an inflammatory infiltrate, consisting mainly of lymphocytes and eosinophils. We present a case of ALHE assessed immunohistochemically for D2-40-a new marker for lymphatic endothelial cells. A biopsy specimen obtained from the same anatomical area of a healthy individual served as a normal control. The ALHE specimen showed increased number of lymphatic vessels when stained for D2-40, whereas the endothelial cells lining blood vessels were negative. The specificity of D2-40 for lymphatic vessels was further substantiated by studying Factor VIII-related antigen expression in consecutive sections of both ALHE and the control specimen. A reverse pattern was appreciated-blood vessels showed Factor VIII positive labeling, whereas lymphatic endothelial cells remained unlabeled. We therefore assume that apart from the lymphocytic infiltrate in the lesion, the recognized lymphoid component in ALHE is due to lymphatic vessel proliferation as well. Hence, this condition may be considered as possibly derived from lymphatic endothelium.