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

Abstract

Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare tumour-like lesion, which occurs in the skin of newborns, principally of the face and neck. RMH has also been reported in unusual sites, including oral cavity, nasal vestibule and vagina. In this case report we describe a rare case of RMH arising as a nodular mass at the anal margin of a male newborn. This is an unusual site for such a rare lesion. The histological examination of the lesion showed the typical features of RMH. Desmin and S100 expression has been determined by immunohistochemical analyses to assess the distribution of the mature skeletal muscle cells and small-sized nerves, which represented the principal components of the nodular mass. Our case emphasizes the possibility that RMH may occur in the perianal region and awareness of this possibility is crucial for pathologists to avoid confusion with other skeletal muscle-containing lesions, especially rhabdomyosarcoma.

Rhabdomyomatous mesenchymal hamartoma presenting as a sacral skin tag in two neonates with spinal dysraphism

“…The vast majority of RMH presented as a small raised lesion on the head or neck. Only five were reported on the lower body, including one on the great toe and four in the anogenital region . This includes one RMH in the buttocks/sacral region of a 2‐day‐old male, which presented as two erythematous atrophic plaques and resolved spontaneously …”

“…Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare malformation with 62 reported cases through 2014 . It was first described in 1986 by Hendrick et al as a striated muscle hamartoma and was later termed RMH by Mills et al in 1989 .…”

Congenital Papule on the Anterior Neck

“…RMH usually presents as a solitary skin lesion of the head and neck, particularly on the nose, chin, periorbital, and anterior neck regions. It has also been reported to occur in unusual sites, including the vagina , toe , oral cavity, nasal vestibule , and anal margin . Although typically a raised lesion, one case of a depressed skin lesion has been reported .…”

Spindle cell lipoma of peri-parotid soft tissues. Report of a case and histogenetic considerations

“…The surgical specimen was submitted for histological examination in neutral-buffered 10% formalin, dehydrated using standard techniques, embedded in paraffin, cut to 5 μm, and stained with hematoxylin and eosin as previously described [10][11][12]. Immunohistochemical analyses were performed using the standard streptavidin-biotin labeling technique (LSAB kit-Dako, Glostrup, Denmark) as previously described [10][11][12].…”

“…Immunohistochemical analyses were performed using the standard streptavidin-biotin labeling technique (LSAB kit-Dako, Glostrup, Denmark) as previously described [10][11][12]. The following antibodies were tested: CD34, CD10 and S-100 protein (all from DakoCytomation, Glostrup, Denmark).…”