Perianal rhabdomyomatous mesenchymal hamartoma.

A rhabdomyomatous mesenchymal hamartoma (RMH) is a rare benign soft tissue tumour found in the face and neck region of children. A three-month-old male infant was referred to our unit with a polypoid anal lesion that had been present from birth. Histopathological examination of the excised sample showed haphazard arrangement of mature striated skeletal muscle in among nerves and blood vessels, and immunohistochemistry confirmed the lesion to be a RMH. There was no evidence of recurrence during the follow-up period. This case emphasises two points: the unique histological characteristics associated with RMH and how this allows distinction from other differential diagnoses, and the consideration of RMH as a diagnosis in perianal lesions.