Calcifying fibrous tumor: a rare case in the foot

Calcifying fibrous tumor is a rare fibroblastic tumor with distinctive histological presentation that shows benign characteristics. To our knowledge, there are no prior reports that have documented imaging findings of calcifying fibrous tumor in the distal lower extremity. We report the case of a 25-year-old man who presented with a mass in the medial aspect of the right foot that was first noted 4 years earlier. Medical attention was sought due to perceived increase in size as well as increasing pain in the right foot. The patient had no limitations in activity but reported worsening discomfort while walking. An anteroposterior radiograph obtained at first presentation demonstrated a large calcified soft mass in the medial aspect of the foot. Contrast-enhanced MRI showed a mildly enhancing 6.5 cm × 2.5 cm × 8.5 cm mass, hypointense on T1- and T2-weighted images, infiltrating the adjacent abductor hallucis and flexor digitorum brevis muscles. Histopathology demonstrated multiple irregular fragments of white-tan firm tissue with a gritty cut surface, positive for CD34 on immunohistochemistry and consistent with calcifying fibrous tumor. Although rare in the extremities, this diagnosis should be considered in patients with a calcifying soft tissue mass. Low signal intensity with low-grade enhancement on MRI as well as stable disease course could prompt a diagnosis of calcifying fibrous tumor even in previously unmanifested locations.