Acute spontaneous tumor lysis syndrome as the initial presentation of ALK-positive diffuse large B-cell lymphoma.

Anaplastic lymphoma kinase (ALK)-positive diffuse large B-cell lymphoma (DLBCL) is a recently described, uncommon form of DLBCL, which has been seen primarily in young men and which presents with advanced disease. The fact that ALK-positive DLBCL is an uncommon diagnosis is likely due to the combined effects of this being an uncommon disease coupled with the challenges in the pathologic identification of this neoplasm. Prompt and accurate identification of this tumor is becoming increasingly important, however, as we enter the era of therapeutic ALK inhibitors, which are currently undergoing study in several clinical trials. Here, we report a case of ALK-positive DLBCL in a 39-year-old male patient who presented with spontaneous tumor lysis syndrome. We review the clinical, morphologic, immunohistochemical, and molecular aspects of this case and of ALK-positive DLBCL in general, with the purpose of bringing to light the existence of this disease and its potential future therapy.