Case Report: Atypical (CD34-) nevus lipomatosus cutaneous superficialis with fibroblastic nodular hyperplasia on the knee.

Nevus lipomatosus cutaneous superficialis (NLCS) is a unique hamartoma, characterized by ectopic adipose tissue in the dermis, which mainly localizes in buttock and thigh. This study elucidates a case of NLCS with fibroblastic nodular hyperplasia and reviews related literature. Herein, a 15-year-old boy was presented with subcutaneous mass consisting of multiple papules on the surface below his left knee joint for 5 years. The histopathological findings revealed ectopic mature adipose tissue and several storiform-arranged masses containing short fusiform cells and mast cells within the dermis and immunohistochemical staining indicated that CD10 was positive in the above fusiform cells. The diagnosis of nevus lipomatosus cutaneous superficialis with fibroblastic nodular hyperplasia was made. This study aims to increase awareness of this rare disease and its concomitant diseases for early recognition and proper treatment strategy.