ALK and diffuse large B-cell lymphoma: This chapter will cover DLBCL, NOS as well as certain DLBCL subtypes (T-cell/histiocyte-rich large B-cell lymphoma; primary cutaneous DLBCL, leg type; and EBV-positive DLBCL, NOS) and related entities (primary mediastinal large B-cell lymphoma, intravascular large B-cell lymphoma [IVLBCL], DLBCL associated with chronic inflammation, lymphomatoid granulomatosis, and ALK-positive large B-cell lymphoma).