An unusual hematopoietic proliferation seen in a nevus sebaceous.

Nevus sebaceous is a tumor of primary epithelial germ cells that is generally first noticed at birth. It is relatively quiescent until puberty when a variety of benign and potentially malignant tumors may arise within it. We describe a nevus sebaceous with immature fat cells, vascular ectasia, and extramedullary hematopoiesis that was present at birth. At 4 months, the immature adipose and hematopoietic elements, as well as the vascular changes, had resolved.