title: Skeletal muscle regeneration: report of a case presenting as a cutaneous nodule following blunt trauma to the lip.
abstract: Skeletal muscle (SM) regeneration is a pleomorphic yet benign reaction pattern that follows injury to SM and has been reported to simulate histologically various malignancies such as squamous cell carcinoma and rhabdomyosarcoma. A 61-year-old man presented with a 4-month history of an enlarging nodule on the upper lip following blunt trauma. An initial punch biopsy was non-diagnostic. A deeper biopsy revealed a multilobular proliferation of atypical and pleomorphic cells with vesicular nuclei, prominent nucleoli, and large amphophilic cytoplasm. Immunoperoxidase studies showed these cells to be positive for muscle-specific actin and desmin and negative for S-100 protein and smooth muscle actin. Based on these findings, a diagnosis of skeletal muscle regeneration (SMR) was made. To our knowledge, this is the first report of SMR presenting clinically as a rapidly growing cutaneous nodule on the lip following blunt trauma.
authors: Department of Dermatology, Dermatopathology Section, Boston University School of Medicine, Boston, MA, USA.
authors: Samer H
authors: SH
authors: Ghosn
authors: Arash
authors: A
authors: Radfar
authors: Catherine M
authors: CM
authors: Stefanato
mesh_terms: D006801:Humans; D007150:Immunohistochemistry; D008046:Lip / Q000293:injuries*; D008047:Lip Diseases / Q000209:etiology* / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology*; D014945:Wound Healing / Q000502:physiology*