Orthopaedic · Radiology · Pathology Conference: Painful Ulnar Lesion in a 16-year-old Boy

Abstract

A 16-year-old boy presented with swelling and a firm painful mass located in the middle of his right forearm 5 weeks after a fall from his bicycle. Immediately after this fall, he had experienced pain, and a contusion of his right forearm was diagnosed in the local emergency department. Gradually, the forearm swelling increased. The pain was mild and did not interrupt sleep. The patient was referred for a second evaluation 3 weeks later in a local public health center. A radiographic assessment of his right forearm (Fig. 1) was performed and the radiographs were erroneously interpreted as normal by a general practitioner, who advised rest. Five weeks postinjury, the symptoms continued and the swelling increased. Physical examination in our hospital revealed a firm mass in his middle forearm, predominantly in the ulnar side, over an area approximately 7 9 7 cm. There was tenderness to palpation and the overlying skin was apparently normal. He was not febrile, had no palpable lymph nodes, and had full motion in the neighboring joints. There was no medical history. Calcium, phosphorus, alkaline phosphatase, and parathormone levels were normal. Plain radiography (Figs. 2, 3A), bone scan (Fig. 3B), multidetector computed tomography (MDCT) (Fig. 4), and MRI (Fig. 5) of the right forearm were performed. Based on the history, physical examination, and imaging studies, what is the differential diagnosis?