Myointimoma of the penis

Myointimoma is an uncommon, benign soft-tissue tumor derived from the intimal cells of blood vessels. Since little is known about this rare tumor entity, our aim is to describe an additional case and to perform the first literature review on this topic. A 49-year-old Caucasian man presented with a 12-month history of a palpable, firm, solitary lesion involving the glans penis. On physical examination, there was a 1 cm palpable, endophytic well-circumscribed nodule located to the left side of glans penis, close to the coronal sulcus, with disease-free external urethral orifice. The patient was submitted to complete excisional biopsy. A skin rhombus measuring 1.1 x 0.8 x 0.3 cm was removed and the biopsy sample, fixed in 10% formaldehyde, sent to Pathology. At the 18-month follow-up visit, the patient was clinically disease free. Histopathology revealed a multinodular intravascular proliferation of the corpus spongiosum. This myointimal proliferation comprised bland predominantly spindle cells in an abundant fibromyxoid stroma. Immunostains for smooth muscle actin (1A4), cytokeratins (AE1/AE3, CAM5.2), and CD34 were carried out using the avidin-biotin complex (ABC) immunoperoxidase method. Lesional cells displayed positivity for smooth muscle actin and negativity for cytokeratins and CD34. Myointimoma is confirmed to be a penile benign lesion that may be adequately treated with excisional biopsy. Even after incomplete or marginal removal, the penile lesion has been shown to remain stable overtime or regress. Differential diagnosis is essential to exclude similar histologic entities that could be more aggressive or have possible systemic implications.