Hairy cell leukemia presenting as localized skeletal involvement.

We report a 45-year-old man who presented with localized skeletal involvement as the initial manifestation of hairy cell leukemia (HCL) without abnormal peripheral blood counts, splenomegaly or posterior iliac crest bone marrow involvement. The patient presented with pain in the left thigh. A plain radiograph was normal, but a magnetic resonance imaging (MRI) of this region showed a marrow-based lesion occupying the left femur neck, left proximal femur and both greater trochanters.