Desmoplastic fibroma of the ulna

Introduction: Desmoplastic fibroma is an extremely rare, locally aggressive, benign bone tumour with incidence of 0.1% of primary bone tumors. It is composed of spindle cells with minimal cytological atypia and abundant collagen. Diagnosis is made on radiology and histopathology. Case Summary: A 17yr female patient presented with pain and swelling in left forearm since 9yrs, slowly progressive in nature. Radiograph showed an osteolytic lesion of the proximal ulna. En-bloc excision was done. Grossly the tumor was 13x6x2.5cm, hard in consistency with grey-white mass on cut section. Microscopically it was composed of spindle shaped cells with elongated bland appearing nuclei arranged in whorled pattern and fascicles with abundant collagen present between spindle cells. No pleomorphism or mitoses were noted. Conclusion: Desmpoplastic fibroma is a very rare locally aggressive benign neoplasm of bone. The diagnosis and management are often difficult and requires a combined speciality approach.