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

Subcutaneous Mass on the Chin of a 15-Year-Old Adolescent Boy: Answer

“…Previous research has indicated that RMH is identified in locations with superficial skeletal muscle, 8 overwhelmingly in the head and neck region. 1,2,5,6,8,10 RMH has also been reported in the truncal, vaginal, and perianal regions. 4,7,11 Treatment in most cases is surgical excision and long-term monitoring for recurrence.…”

“…Numerous reports have outlined specimens with diffuse muscle-specific actin expression, [5][6][7]9 as well as anti-desmin antibody positivity. 9 Vascular and adnexal elements have also been noted in several cases, 1,2,4,6,8,9 and Sayan et al described a mass with significant anti-CD-68 antibody positivity, illustrating the presence of histiocytes. 9 Although these masses exhibit disordered growth of multiple cell types, they are benign, they do not exhibit a high proliferative index, 9 and there are no reports of associated malignancy.…”

“…Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare, congenital skin mass most notably seen in infants and young children, with less than 85 reported cases worldwide. 1,2 Although first described by Hendrick et al in 1986 as a striated muscle hamartoma, 3 further research has shown that striated muscle fibers, adipose tissue, 1,2,4-7 nervous tissue, 1,2,[4][5][6]8 and connective tissue elements 5,6,8 in differing ratios can be present on histopathologic examination. Numerous reports have outlined specimens with diffuse muscle-specific actin expression, [5][6][7]9 as well as anti-desmin antibody positivity.…”

Rhabdomyomatous Mesenchymal Hamartoma: Report of 4 Cases With Histochemical and Immunohistochemical Findings and Emphasis on Potential Pitfalls

“…Some of the reported cases could have represented lipomatous, fibromatous, or trauma-related lesions. 14,[17][18][19] The authors have described noncongenital, posttraumatic deep soft-tissue lumps without skin involvement in adults as RMHs. The histopathologic images, however, showed features suggestive of an intramuscular lipoma with abundant adipose lobules or a traumatic neuroma with prominent thickened nerve bundles.…”

“…There are examples of RMHs in children and adults, but in many of these reports, the possibilities of other muscle-containing look-alike lesions were not adequately excluded (Table 2). 11–19 Some of the reported cases may reflect intramuscular vascular lesions. 11,13,15,16 In our retrospective review, 2 cases that were initially labeled as RMHs were excluded because re-review of the slides has shown features of intramuscular angiomas (Table 2).…”