Primary lymphoma of bone of the little finger: a case report and review of the literature.

Primary lymphoma of bone (PLB) is a rare, malignant lymphoid proliferation within bone accounting for less than 3% of all malignant bone tumors. In this case report, a 61-year-old female with past medical history of gout presented with pain and swelling in her right little finger. Initial radiographs demonstrated periostitis and soft tissue swelling about the right little finger. She returned three months later with progressive pain. Subsequent MRI and repeat radiographs demonstrated near complete destruction of the right little finger middle phalanx and periostitis with marrow infiltration at the right long finger. Given the rapid progression of disease, the differential diagnosis consisted primarily of aggressive neoplastic processes. The little finger ray was amputated through the level of the metacarpophalangeal joint and histopathology demonstrated large neoplastic cells that stained positive with CD45, CD20, and PAX5, compatible with diffuse large B-cell lymphoma. A subsequent normal bone marrow aspiration and PET-CT demonstrated no additional sites of disease, thus excluding secondary lymphoma to bone. To the best of our knowledge, this is the first case report of polyostotic PLB involving the hand. PLB of the hands may be initially misdiagnosed due to its rarity and clinical presentation mimicking rheumatological disease. Clinical vigilance in concert with close imaging follow-up is required to make the diagnosis in a timely fashion. We also review the existing PLB hand literature which consists of five cases.