Presentation
Incidental finding after trauma.
Patient Data
There is a central medullary geographic lytic lesion at the base of the fifth proximal phalanx measuring up to 12.7 x 9.1 mm (Long x trans), with predominantly sharp and non-sclerotic margins and some indistinct margins distally at the transition with the midshaft. There is a ground glass like appearance of the lesion matrix, but no chondroid or osteoid matrix. No bone expansion or cortical breach. No other lesions seen. Bones are otherwise normal. Joint spaces and alignment are preserved. No soft tissue abnormalities.
Case Discussion
The imaging features are those of a low aggressive lesion, and differentials would include enchondroma and fibrous dysplasia.
The lesion was biopsied: Sections show three pieces of tissue comprised of immature woven bone with broad osteoid seams around central calcified areas, surrounded by fibrous tissue with a few osteoclasts and scattered small vessels. There is no inflammation or atypia. No cartilage is present. There is no evidence of malignancy.
DIAGNOSIS: Right little finger proximal phalanx biopsy: Fibrous dysplasia.