Biopsy‐Proven Spontaneous Regression of a Rhabdomyomatous Mesenchymal Hamartoma

Abstract

Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare, benign, congenital tumor of the dermis and subcutaneous tissue comprised of skeletal muscle and adipose and adnexal elements. Although the majority of cases are an incidental finding in otherwise healthy patients, some have been reported in association with other anomalies. We present a full-term boy evaluated on day 2 of life for two lesions located on the midline of the lower back and right buttock that each appeared clinically as an atrophic, pink plaque. Ultrasound of the midline lesion revealed an underlying lipomyelomeningocele with a tethered cord in the spinal canal. Histopathology of the right buttock cutaneous lesion was consistent with a diagnosis of RMH. Surgical excision was performed on the midline intradural lipoma and the lesion on the buttock was monitored clinically. Repeat biopsy of this site at 1 year of age revealed complete spontaneous regression. This case highlights three interesting features: the association with an occult spinal dysraphism lipomyelomeningocele and tethered cord, the clinical presentation of an atrophic plaque as opposed to the more commonly reported raised lesions, and the phenomenon of spontaneous regression of the lesion. Most importantly, this final feature of regression in our patient suggests that, in the absence of symptoms, clinical observation of RMH lesions is warranted for spontaneous regression for 1 to 2 years provided that no functional deficit is noted and that the cutaneous or deeper lesions are not causing a medical problem.

Rhabdomyomatous Mesenchymal Hamartoma: A Deep Subcutaneous Lesion in the Sternoclavicular Area

“…Rhabdomyomatous mesenchymal hamartoma (RMH), previously described in 1986 as striated muscle hamartoma, is a rare cutaneous hamartoma occurring particularly in the head and neck region . Forty‐seven cutaneous cases have been reported in the literature .…”

A review of eight unusual pediatric skin and soft-tissue lesions: Diagnosis, workup, and treatment

“…The lesion is usually excised, but spontaneous regression has been reported. 43,46 Recurrence after excision is not reported.…”

“…38 It may be associated with cleft lip, ocular abnormalities (including Delleman's syndrome and Goldenhar syndrome), thyroglossal duct sinus, amniotic band syndrome, spinal dysraphism, or trauma. 43,44 Diagnosis warrants systemic evaluation for other congenital lesions. The lesion is usually excised, but spontaneous regression has been reported.…”

“…43,44 RMH may be derived from the aberrant migration of skeletal muscle fibers into the dermis during embryogenesis. 38 It may be associated with cleft lip, ocular abnormalities (including Delleman's syndrome and Goldenhar syndrome), thyroglossal duct sinus, amniotic band syndrome, spinal dysraphism, or trauma.…”

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

“…Clinically, it can present as small dome-shaped papule or a polypoid pedunculated lesions [1][2][3][4][5][6][15][16][17][18][19]. Notably, rare cases of RHM may undergo spontaneous regression [20,21]. The etiology of RMH is still unclear, but it is likely that an aberrant embryological development or migration of mesodermally derived tissues due to microenvironmental modifications and/or genetic factors may play a pathogenetic role.…”