Solitary Infantile Myofibromatosis; Differential Diagnosis of Solitary Frontal Bone Lytic Lesion in Neonatal Period

Abstract

Background: Infantile myofibromatosis (IM) is the most common benign fibrous soft tissue tumor found in infants, presenting either as a single lesion (solitary) or multiple lesions (multicentric) that can affect the skin, muscles, bones, or internal organs. While bone involvement is typically associated with the multicentric form or craniofacial bones in solitary cases, it rarely appears in the extremities, where it radiologically presents as a well-defined, bone-dissolving lesion surrounded by a hardened border.

Case Presentation: A 6-month-old male infant with a congenital left frontal bone swelling. Radiological evaluation revealed a well-circumscribed, expansile lytic skull lesion with no internal extension or abdominal masses. Complete surgical excision and subsequent microscopic and immunohistochemical examination confirmed the benign diagnosis, showing a characteristic biphasic pattern of SMA positive, spindle-shaped cells and vascular spaces without any signs of malignancy.

Conclusion: By combining clinical observations and imaging with characteristic biphasic microscopic features, solitary infantile myofibromatosis can be accurately identified and differentiated from similar spindle cell tumors, ensuring a positive outlook for the patient.