Rhabdomyomatous mesenchymal hamartoma: an unusual dermal entity with a report of two cases and a review of the literature

Abstract

RMH is a rare benign condition of the deep dermis and subcutaneous fat with only 22 cases existing in the English literature. To our knowledge, this is the first report of an elderly man presenting with RMH, presumptively present since birth. There was no evidence of cellular or malignant degeneration. While the etiology of RMH is unknown, possible explanations include aberrancy in the embryonic migration of mesodermally derived tissues or a genetic defect predisposing to the formation of hamartomas.

Rhabdomyomatous mesenchymal hamartoma: a case report

“…Microscopically these lesions are constituted by striated muscle fibers randomly distributed, intermingled with mature adipose tissue, collagen bands, blood vessels, and elastic fibers (1,16) . Adnexal structures interwoven with the muscle bundles are reported.…”

“…The neuromuscular choristoma (benign Triton tumor) is a subcutaneous lesion composed of skeletal muscle fibers and neural tissue (13) . The rhabdomyoma contains variable amounts of myxoid and fibrous tissue, with mesenchymal undifferentiated cells and fetal striated muscle (8,16) . Lastly, the cutaneous embryonal rhabdomyosarcoma represents a rare and much less differentiated entity (4,20) .…”

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

“…The term "hamartoma", first coined by Mills in 1989 [1], has been histologically proven, being this lesion composed of a disordered mixture of mature adipose and skeletal muscle tissue, adnexal structures and sometimes blood vessels and nerves [4]. Although RMH is usually a solitary lesion, it can present as multiple lesions [7], rarely in association with uncommon congenital abnormalities [8,9].…”

“…Rhabdomyomatous mesenchymal hamartoma (RMH) is a raretumour-like lesion, which occurs in the skin of newborns, principally of the face and neck [1][2][3][4][5][6]. The term "hamartoma", first coined by Mills in 1989 [1], has been histologically proven, being this lesion composed of a disordered mixture of mature adipose and skeletal muscle tissue, adnexal structures and sometimes blood vessels and nerves [4].…”

“…Apart from the skin of the head and neck region, RMH has also been reported in unusual sites, including oral cavity [15][16][17], nasal vestibule [18] and vagina [19]. 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].…”