ALK-positive diffuse large B-cell lymphoma: report of four cases and review of the literature.

We report detailed clinical and pathologic features of four cases of anaplastic lymphoma kinase-positive diffuse large B-cell lymphoma (ALK-DLBCL), a rare entity with only 29 currently reported cases. This study is the third largest of all reported series. Biopsies from four adult patients aged 41, 49, 53, and 71 years (three lymph nodes and one nasopharyngeal mass) exhibited immunoblastic/plasmablastic morphology. By immunohistochemistry and/or flow cytometry, they expressed cytoplasmic ALK-1, CD138, VS38 (3/3), monoclonal cytoplasmic light chain, CD45, EMA, CD4, and CD57 (2/3), and were negative for CD3, CD30, CD56, and TIA-1. Two showed variable CD79a expression, and one had rare CD20(+) cells. Two of three cases exhibited rare CD43(+) reactivity. One case showed scattered cytokeratin(+) cells, which could possibly lead to a misdiagnosis of carcinoma. After CHOP and radiotherapy, two stage I patients were free of disease at 58 and 36 months, whereas a stage IV patient was dead of disease at 22 months.