Desmoplastic Fibroma of the Ulna Bone: A Case Report of a 16-Year-Old Girl.

Desmoplastic fibroma (DF) is a rare, benign, yet locally aggressive bone tumor, typically affecting long bones in young individuals. Its occurrence in the ulna is extremely rare. This case report highlights the diagnostic challenges of a 16-year-old female presenting with DF of the ulna. The report emphasizes individualized treatment and long-term follow-up and raises awareness of DF in atypical locations. This patient presented with a two-month history of mild, activity-related pain in the distal forearm. Imaging revealed an expansile lytic lesion in the distal ulna, characterized by cortical thinning and breaches, consistent with desmoplastic fibroma (DF). Routine blood tests were normal, and histopathology confirmed spindle fibroblasts in a collagenous stroma with dilated vascular channels, confirming DF. The patient underwent intralesional curettage, bioceramic cement application, and plate and screw fixation. Postoperatively, she experienced mild surgical site pain but retained full wrist motion and grip strength. At six months, the patient showed no recurrence and good functional outcomes. This case highlights the rarity of desmoplastic fibroma in the ulna, emphasizing the challenges of diagnosis and management. Accurate diagnosis through imaging and histopathology, combined with individualized surgical treatment, preserved function and prevented reoccurrence. It underscores the need for long-term follow-up to ensure successful outcomes and adds valuable insight to the limited literature on this condition.