A 4-month-old boy presented with swelling of the right forearm that he had experienced for 2 months. His parents had previously consulted another hospital 1 month prior where fine-needle aspiration cytology showed only inflammatory cells. The child was brought to our hospital as the swelling continued to progress in size. The child was afebrile, and there were no other swellings.
Clinical examination showed diffuse, hard, immobile, and nontender swelling over the proximal aspect of the dorsal surface of the forearm. The swelling was 6 cm by 3 cm in size over the ulna (Fig. 1). Movements of the elbow and wrist and pronation and supination were normal. Radiographs of the forearm showed the lytic area in the ulna surrounded by sclerotic bone (Fig. 2). Blood examination showed normal white blood cell counts, erythrocyte sedimentation rate, C-reactive protein, and alkaline phosphatase.
Magnetic resonance imaging (MRI) of the forearm showed altered marrow signal noted in the middle third to the proximal third diaphysis of the ulna with an adjacent, fairly defined, soft-tissue mass at the medial aspect. The medial cortex of the ulna was eroded with areas of periosteal new bone formation.
An open biopsy was performed, and, on exposure, the ulnar black tissue was seen under the periosteum and was eroding the ulna (Fig. 3). The tissue was removed, and histopathology showed fibrous tissue containing irregular clusters of cells in a fibrillary matrix and clusters of cells containing pigment granules (Figs. 4, 5, and 6).
Scan by WeChat
