Imaging Findings Of Desmoplastic Fibroma Rarely Involving The Clavicle: Case Report
A 28-year-old man, with a history of sudden right shoulder pain during forceful flexion of his upper arm visited our hospital complaining of tenderness, resting pain, and limitation of range of motion due to pain. Initial work-up with plain radiograph demonstrated an oval shaped osteolytic lesion on the medial one-third of the right clavicle with pathologic fracture (). Further evaluation with MRI was done after 10 days (). The lesion showed hypointense to isointense signal compared to its adjacent muscle on T1-weighted images, and hypointense to isointense signal on T2-weighted images. After intravenous gadolinium contrast administration, the lesion presented heterogeneous enhancement. The mass showed a expansile bulging contour with endosteal erosion and periosteal reaction with enhancement. The aggressiveness of the tumor could not be evaluated easily due to the combined fracture. Our initial impression was benign primary bone tumor with low aggressiveness rather than malignant tumor. However, the patient was lost to follow up. Two years later, he came back to our hospital due to pain. Excisional biopsy was done. Histologically, the tumor was generally hypocellular to moderately cellular and composed of bland fibroblasts in a background of numerous thick and wavy collagen fibers. Thin spicules of residual trabecular bone with reactive changes were presented within the tumor. Multiple sections of the tumor presented no evidence of cellular pleomorphism, changes in the nuclear cytoplasmic ratio, nuclear hyperchromasia, or mitotic activity. Despite its bland appearance, the tumor showed multifocal soft tissue extension (). These findings resembled those of soft tissue desmoids. Thus, the tumor was diagnosed as a desmoplastic fibroma of bone, which is considered as an intraosseous counterpart of soft tissue desmoids. Finally, a wide resection including the lesion and adjacent tissues was done with an allogenous fibular bone graft and an autogenous corticocancellous iliac bone graft.