Solitary infantile myofibroma of the orbital bone.

Infantile myofibroma of the orbit is an extremely rare condition. Only a few instances of this condition have ever been reported. A 3-year-old boy visited our clinic with lateral lower eyelid swelling and a palpable mass in the left eye, which had apparently persisted for 2 months. A computed tomography scan revealed a well-circumscribed mass in the inferolateral orbital portion of the zygomatic bone, coupled with erosion of bone and orbital extension with reactive hyperostosis. Immunohistochemical stains proved positive for smooth muscle actin, supporting the diagnosis of solitary infantile myofibroma of the orbital bone (zygoma). Although rarely found in the orbit, solitary infantile myofibroma can display more aggressive or malignant neoplasm. Immunohistochemistry is integral to the differential diagnosis and a systemic evaluation for multicentric myofibroma is essential.