title: Cutaneous mesenchymal hamartoma with mixed myogenous differentiation.
abstract: A 3-month-old infant girl presented with a polypoid lesion in the perianal region. No changes in this lesion had been noted since birth. Microscopic examination of the excised specimen showed a mixture of mesenchymal elements, dominated by haphazard thin fascicles of skeletal muscle. Collagen and vascular changes were also apparent. Immunohistochemistry showed positive staining for muscle-specific actin and desmin in the fascicular components of the lesion, and smooth muscle actin, desmin, and h-caldesmon positivity in a haphazard collection of muscle fibers in the deep dermis and anal submucosa. Numerous Verhoeff-van Gieson positive elastic fibers were also noted. Hamartomas containing skeletal muscle have rarely been reported outside of the head and neck region. They must be distinguished from a variety of other tumors, including juvenile rhabdomyoma, benign Triton tumor, and rhabdomyosarcoma.
authors.affiliation: Division of Surgical Pathology, University of Virginia Medical Center, Charlottesville, VA 22908-0214, USA.
authors.forename: John Edwin
authors.initials: JE
authors.lastname: Schrecengost
authors.forename: Sana
authors.initials: S
authors.lastname: Tabbara
authors.forename: James
authors.initials: J
authors.lastname: Patterson
authors.forename: Mark R
authors.initials: MR
authors.lastname: Wick
mesh_terms: D002454:Cell Differentiation; D020405:Dermis / Q000473:pathology*; D005260:Female; D006222:Hamartoma / Q000151:congenital / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D007223:Infant; D008648:Mesoderm / Q000473:pathology*; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000473:pathology