Cutaneous mesenchymal hamartoma with mixed myogenous differentiation

Abstract

A 3-month-old infant girl presented with a polypoid lesion in the perianal region. No changes in this lesion had been noted since birth. Microscopic examination of the excised specimen showed a mixture of mesenchymal elements, dominated by haphazard thin fascicles of skeletal muscle. Collagen and vascular changes were also apparent. Immunohistochemistry showed positive staining for muscle-specific actin and desmin in the fascicular components of the lesion, and smooth muscle actin, desmin, and h-caldesmon positivity in a haphazard collection of muscle fibers in the deep dermis and anal submucosa. Numerous Verhoeff-van Gieson positive elastic fibers were also noted. Hamartomas containing skeletal muscle have rarely been reported outside of the head and neck region. They must be distinguished from a variety of other tumors, including juvenile rhabdomyoma, benign Triton tumor, and rhabdomyosarcoma.

Rhabdomyomatous mesenchymal hamartoma presenting on a digit

“…To our knowledge, there have been only two reports describing rhabdomyomatous mesenchymal hamartomas outside the head and neck. Both of those lesions were present perianally 14,23 . We report a rhabdomyomatous mesenchymal hamartoma occurring in a novel location, thereby expanding the clinical spectrum of this uncommon lesion.…”

“…In the original report by Hendrick et al, the two patients were newborns, one of whom had amniotic band syndrome 1 . Since then, there have been a total of 29 cases reported in the literature, with the vast majority of lesions occurring on the head and neck in very young patients 2–23 . To our knowledge, there have been only two reports describing rhabdomyomatous mesenchymal hamartomas outside the head and neck.…”

Rhabdomyomatous mesenchymal hamartoma (RMH) of the anal region: an unusual location for such a rare lesion

“…Although the two cases of perianal RMH reported in the literature were described as having a polypoid configuration [8,22], interestingly our case presented clinically as a dome-shaped nodule. Differential diagnosis of RMH mainly revolves around fetal rhabdomyoma and embryonal rhabdomyosarcoma.…”

“…This is an unusual site for such a rare lesion, with only two cases previously reported in the peri-anal skin [8,22].…”

Perianal rhabdomyosarcoma presenting 21 months after hamartoma excision

“…Hamartomatous lesions can occasionally present with myogenous differentiation, and this has been described in the perianal region [7,8]. Rhabdomyomatous mesenchymal hamartoma (RMH) of the skin would be an example.…”