Anaplastic lymphoma kinase protein positive diffuse large B cell lymphoma; A developing world experience

Anaplastic lymphoma kinase (ALK) positive diffuse large B-cell lymphoma (ALK + DLBCL) is a rare, distinct and aggressive subtype of non-Hodgkin's lymphoma (NHL). These tumors are considered to be derived from post-germinal center B cells but peculiarly their distinction is based on the fact that they are ALK-positive neoplastic B cells but lack expression of B cell markers (CD19,CD20, CD79a), T cell markers (CD3, CD5) and CD30. Its broad differential diagnosis and similarities to plasmablastic lymphoma, immunoblastic DLBCL, Anaplastic large-cell lymphoma (ALCL) of T-null cell lineage, and poorly differentiated/anaplastic carcinoma pose a grave challenge to physicians with conventional costly treatment for DLBCL failing to yield any clinical or prognostic significance in ALK + DLBCL. In this article we present 7 cases which were reported at Aga Khan University Hospital, Department of Pathology and Laboratory Medicine from 2009 to 2015 and a review of literature on ALK+ DLBCL, which according to the best of our knowledge is the second largest reported series and the first from South Asian subcontinent.