Abstract

Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare congenital tumor of the dermal and subcutaneous tissues, presenting as a midline, often pedunculated, papule on the head and neck. It was first described as “striated muscle hamartoma” by Hendrick et al. (1986) and there are only 67 cases reported in the literature. Herein we report two cases of RMH. The first case is a 12-year-old male with autism and neurofibromatosis type 1 who presented with a 5-6 mm, slightly pink papule on his nose that was gradually increasing in size over 10 years. He underwent excision and histopathological examination showed skeletal muscle fibers admixed with mature adipose tissue, adnexal structures and neurovascular bundles in a haphazard manner compatible with a diagnosis of RMH. The second case is a 48-day-old male who presented with a 4 mm firm, non-tender, smooth, mobile nodule on the upper cutaneous lip just lateral to the philtrum which was first noticed at birth. He underwent excision at 9 months of age with histopathology consistent with RMH. While RMH is a benign neoplasm, it may be associated with other congenital anomalies. The histologic differential diagnosis includes neuromuscular choristoma (also known as benign triton tumor), fetal rhabdomyoma, rhabdomyosarcoma, nevus lipomatosus superficialis and fibrous hamartoma of infancy. Our cases prompt clinicians and pathologists to consider RMH in the differential diagnosis of congenital midline facial lesions with skeletal muscle differentiation and add two additional cases of this rare entity to the literature.

Financial Disclosure:
No current or relevant financial relationships exist.