fibrous hamartoma of infancy

Fibrous hamartoma of infancy

Fibrous hamartoma of infancy (FHI) is a rare, typically painless, benign tumor that develops in the subcutaneous tissues of the axilla (i.e. armpit), arms, external genitalia, or, less commonly, various other areas. It is diagnosed in children who are usually less than 2 years old or, in up to 20% of cases, develops in utero and is diagnosed in an infant at birth. The cells involved in FHI include bland fibroblasts, myofibroblasts, mature fat cells, and primitive-appearing spindle-shaped and/or star-shaped cells. The tumor was first described by R.D. Reye in 1956 who termed the disorder "subdermal fibromatous tumor of infancy" and regarded it as a reactive lesion. In a 1964 study of 30 patients, F.M. Enzinger renamed the tumor hamartoma of infancy; he regarded it to be a hamartoma (i.e. a local malformation of various normal cell types due to a systemic genetic condition) rather than a reactive lesion. However, subsequent studies have found gene mutations in FHI tumor cells and conclude that it is a true neoplasm, i.e. a growth of cells which is uncoordinated with that of the normal surrounding tissue and persists in growing abnormally even if the original trigger is removed. In 2020, the World Health Organization classified FHI in the category of benign fibroblastic and myofibroblastic tumors. Fibrous hamartoma of infancy is generally a benign tumor but may be locally aggressive, locally infiltration, and in uncommon cases produce symptoms such as tenderness. Surgical excision is the treatment of choice for FHI tumors.