Fibrous hamartoma of infancy of the labium majus: a typical lesion in an unusual site

Fibrous hamartoma of infancy is a soft tissue subdermal fibromatous tumour that characteristically occurs in the first years of life. It is histologically composed of three different components that are intimately admixed: well-defined bundles of fibro-myofibroblastic spindle-shaped cells, nodular proliferations of immature-looking mesenchymal cells set in a myxoid stroma, and mature adipose tissue. A wide intralesional and interlesional cellular composition is commonly observed. Fibrous hamartoma of infancy usually arises from subcutaneous tissue of the trunk, axilla, upper extremities and inguinal region. Only rarely has fibrous hamartoma of infancy been reported in genital organs, with only one case described in the labium majus. We report a rare case of fibrous hamartoma of infancy in the labium majus of a 1-year old female child. Ultrasonography revealed the presence of a mass-like lesion involving subcutaneous tissue, with ill-defined margins. We emphasize that fibrous hamartoma of infancy should be included in the differential diagnosis of soft tissue tumour-like and tumour lesions of the vulva in children. Awareness that fibrous hamartoma of infancy occurs at this site with irregular margins is important to avoid confusion with other lesions exhibiting a more aggressive behaviour.