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.