Penile myointimoma in children and adolescents: a clinicopathologic study of 5 cases supporting a distinct entity

Penile myointimoma is a rare benign myointimal proliferation occurring exclusively within the corpus spongiosum of the glans penis and is most commonly described in adult patients. To date, there is only one reported series of 10 penile myointimomas plus one case report, representing a total of 8 adults and 3 children/adolescents. We report 5 penile myointimomas occurring in 5 patients less than 18 years of age (age range 4 to 15 y). All patients presented with a mass lesion on the glans penis ranging in size from 0.4 to 1.8 cm. All 5 lesions had the classic morphologic appearance: myointimal proliferation of the preexisting vascular spaces of the corpus spongiosum, creating a multinodular/plexiform architecture. Immunohistochemically, all stained cases showed strong cytoplasmic immunoreactivity for smooth muscle actin in the lesional cells and a collarette of native smooth muscle highlighted by desmin. None of the lesions appeared completely excised, but all 5 patients were clinically free of disease at last clinical follow-up (2 to 45 mo). In summary, we report only the second series of this distinctive, relatively rare myointimal proliferation within the corpus spongiosum of the glans penis, expand the number of published cases occurring in the pediatric/adolescent population, and confirm the benign clinical course after a marginal or incomplete excision.