Plaque‐Type Variant of Acquired Rhabdomyomatous Mesenchymal Hamartoma on the Chin: A Case Series

Abstract

Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare benign tumor composed of skeletal muscle fibers and other mesenchymal-derived cells. The lesions are generally solitary sessile papules or skin tag lesions that occur during childhood. We retrospectively reviewed patients diagnosed with RMH pathologically between January 2001 and June 2020 at a tertiary medical center. A literature review was conducted. Seven plaque-type RMHs on the chin were found, including 6 in adults and one in a 14-yearold boy. The average age was 45.7 years. The onset of the RMH appearance was between several months and years. Pathologically, all patients showed a scattered haphazard arrangement of skeletal muscle bundles in the dermis and/or subcutis. Subcutis replaced by fibrous tissue and skeletal muscle bundles was present in 2 cases. Some skeletal muscles had a periadnexal distribution. This case series demonstrated a distinct clinical presentation of acquired RMH specifically located on the chin.

A rare adult presentation of a congenital tumor discovered incidentally after trauma

“…RMH is a rare, congenital, benign tumor historically seen on the midline of the face and neck, and complete removal of the tumor has been the course of action among the 80 documented cases. 1 , 5 , 6 It can appear as a subcutaneous growth or plaque grossly, and it is a histopathologically determined mixture of haphazard skeletal muscle, adnexal elements, vessels, and nerve bundle collections. 7 Among the few documented cases, there is 1 known case of congenital RMH to have regressed after the decision was made to monitor.…”

Yellowish nodule with hypertrichosis on the upper lip

“…Histologically, RMH is characterized by circumscribed proliferation of regularly configured adipose tissue, skeletal muscle, adnexal structures, blood vessels, and/or neurons [1,[7][8][9]. These tissue types are nonorganized and variably arranged, typically with prominent striated muscle fibers [3,8,9].…”

“…Histologically, RMH is characterized by circumscribed proliferation of regularly configured adipose tissue, skeletal muscle, adnexal structures, blood vessels, and/or neurons [1,[7][8][9]. These tissue types are nonorganized and variably arranged, typically with prominent striated muscle fibers [3,8,9]. The variable pattern of tissues in RMH leads to a wide range of histologic differential diagnoses, such as lipomatous tumors, rhabdomyomas/rhabdomyosarcomas, hemangiomas, or even nevus sebaceus (Table 1).…”

Gelblicher Knoten mit Hypertrichose an der Oberlippe

“…Histologisch ist das RMH durch umschriebene Proliferation von regelhaft konfiguriertem Fettgewebe, Skelettmuskulatur, Adnexstrukturen, Blutgefäßen und/oder Nervenzellen gekennzeichnet [1, [7][8][9]. Diese Gewebetypen sind nicht organisiert und variabel angeordnet, wobei prominente quergestreifte Muskelfasern typisch sind [3,8,9].…”

“…Histologisch ist das RMH durch umschriebene Proliferation von regelhaft konfiguriertem Fettgewebe, Skelettmuskulatur, Adnexstrukturen, Blutgefäßen und/oder Nervenzellen gekennzeichnet [1, [7][8][9]. Diese Gewebetypen sind nicht organisiert und variabel angeordnet, wobei prominente quergestreifte Muskelfasern typisch sind [3,8,9]. Die wechselnde Ausprägung der Gewebe in RMH führt zu einem breiten Spektrum histologischer Differenzialdiagnosen, wie lipomatösen Tumoren, Rhabdomyome/Rhabdomyosarkome, Hämangiome oder auch Naevus sebaceus (Tabelle 1).…”