Rapidly growing subcutaneous mass in an infant.

Fibrous hamartoma of infancy (FHI) is a benign mesenchymal tumor of young children. It has a broad clinical differential diagnosis and is often clinically confused for vascular and malignant soft tissue neoplasms. Recognition of the unique histologic features of FHI, a triphasic population of mature adipose tissue, mature fibrous tissue, and immature mesenchymal tissue, will ensure the correct diagnosis. In this report we present a case of this rare entity, including the associated clinical, radiologic, and histologic findings.