Rhabdomyomatous Mesenchymal Hamartoma of Skin

Abstract

A 4-year-old boy was seen at the Kanto Teishin Hospital because of a lesion present at birth. Examination revealed a round, soft, soybean-sized, pedunculated nodule on the midline anterior neck region. Histologically, the most conspicuous aberration was the presence of bundles of striated skeletal muscle fibers throughout the dermis. This nodule was diagnosed as rhabdomyomatous mesenchymal hamartoma of skin, a name first given by Mills. We believe this is the first report of this condition inJapan.

Rhabdomyomatous mesenchymal hamartoma presenting on a digit

“…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.…”

Cutaneous mesenchymal hamartoma with mixed myogenous differentiation

“…The histopathologic image of these lesions features randomly arranged mature skeletal muscle fibers, interspersed with other mesenchymal tissues including collagen bundles, adipose tissue, nerves, and blood vessels. Such proliferations were initially described by Hendrick et al in 1986 6 and were called ‘skeletal muscle hamartomas’ they were later renamed ‘rhabdomyomatous mesenchymal hamartomas’ 7–12 or ‘congenital midline hamartomas’ 13 …”

“…The clinical appearance is that of a pedunculated polyp, or, more uncommonly, a subcutaneous nodule measuring up to 2 cm in maximum dimension; 5–16 sometimes, several independent lesions are seen 9 . The generally small size of myomatous cutaneous hamartomas implies that those in superficial locations tend to be detected preferentially.…”

“…5 The histopathologic image of these lesions features randomly arranged mature skeletal muscle fibers, interspersed with other mesenchymal tissues including collagen bundles, adipose tissue, nerves, and blood vessels. Such proliferations were initially described by Hendrick et al in 1986 6 and were called 'skeletal muscle hamartomas' they were later renamed 'rhabdomyomatous mesenchymal hamartomas' [7][8][9][10][11][12] or 'congenital midline hamartomas'. 13 The clinical appearance is that of a pedunculated polyp, or, more uncommonly, a subcutaneous nodule measuring up to 2 cm in maximum dimension; [5][6][7][8][9][10][11][12][13][14][15][16] sometimes, several independent lesions are seen.…”

A Flesh‐Colored Papule on the Neck of a Child

“…Approximately 18 cases of striated muscle hamartoma have been reported in the literature ( 1–11). This entity has also been reported under the name rhabdomyomatous mesenchymal hamartoma ( 3–5, 7, 10, 11). It is a congenital lesion seen in both males and females of all races.…”