Isolated infantile myofibroma of the calvarium: Report of a case with a literature review.

Objective: Infantile myofibromatosis is a rare entity of childhood characterized by benign myofibroblastic tumors in the soft tissues, the bones, and occasionally the viscera. Solitary skeletal lesions are relatively uncommon. Calvarial involvement should be distinguished from more aggressive tumors for appropriate treatment.

Methods: We reviewed solitary infantile myofibroma of the calvarium and discussed the relevant computed tomography and magnetic resonance imaging findings along with differential diagnosis. A case study of the frontal bone in a 5-month-old girl was also presented.

Results: Fourteen cases were reviewed, including the current case. Of the 13 cases with known sex, eight were male and five female. The mean age was 3.03 with an age range of 0.41-9 years. Nine of the 14 tumors were in the frontal bone. The lesions were intradiploic with tabula interna and/or externa of the calvaria involvement. The mean largest diameter was 22.3 mm. Upon computed tomography, all the lesions were expansile and lytic, and hypoattenuated, isoattenuated or occasionally hyperatenuated. Calcification was not seen. On magnetic resonance imaging, most neoplasms were hypointense on T1-weighted and T2-weighted images. Neoplasms showed hypointense signal on diffusion-weighted imaging and hyperintense on apparent diffusion coefficient, without restricted diffusion in three cases. All lesions were intensely enhanced after gadolinium administration. Treatment was total surgical resection and recurrence was not observed during follow-up.

Conclusions: Infantile myofibromas are rare, typically intradiploic expansile lytic lesions with tabula interna and/or externa involvement. Distinctive imaging features include the presence of hipointense signals on T2-weighted magnetic resonance images without restricted diffusion on diffusion-weighted imaging. A slow-growing, firm, painless, and nontender mass with supportive imaging findings should raise suspicion of the disease.