Fibrous hamartoma of infancy: current review

This review examines 197 cases of fibrous hamartoma of infancy (FHI) described in the literature and provides a detailed clinicopathologic analysis of what is known to date of this peculiar lesion of the subcutis and lower dermis. The vast majority of these cases occurred within the first year of life (91%). Twenty-three percent were congenital. There was a predilection for boys with a male/female ratio of 2.4. Males and females had similar anatomic distribution with the most common locations being the axillary region, upper arm, upper trunk, inguinal region, and external genital area. Most cases presented as solitary masses, but four cases of multiple separate synchronous lesions have been reported. Most lesions presented as a painless nodule, sometimes with rapid growth. A few cases had overlying skin changes, including alteration in pigmentation, eccrine gland hyperplasia, and increased hair. No lesions were reported to have familial or syndromic association, or to occur in combination with other hamartomas. Spontaneous regression has not been reported. The treatment of choice is local excision. Even with incomplete excision, FHI has a low recurrence rate. Criteria for histologic diagnosis include the presence of well-defined bundles of dense, uniform, fibrous connective tissue projecting into fat, primitive mesenchyme arranged in nests, concentric whorls or bands, and mature adipose tissue intimately admixed with the other components. Flow-cytometric and conventional cytogenetic studies have not been reported; these may clarify any relationship to other fibroblastic/myofibroblastic proliferations in children, resulting in better classification and terminology of this unique lesion.