Collision dermatosis: angiolymphoid hyperplasia with eosinophilia developing within a congenital port wine nevus

This is the report on a 22-year-old man suffering since birth from a port wine nevus at his left shoulder, which at the age of 21 showed slight thickening in the central area of the lesion. Histology revealed typical features of nevus flammeus at the border zone and in the newly developing central area proliferation of dilated vessels with prominent endothelial walls surrounded by dense lymphoid cell infiltrates containing many eosinophils and lymph-follicle-like structures in the mid and deep dermis, compatible with angiolymphoid hyperplasia with eosinophilia (ALHE). This is the first report of ALHE occurring in a congenital port wine nevus indicating microenvironmental importance for vascular reactive or neoplastic proliferations. The relationship to Kimura's disease will be discussed.