T-cell/histiocyte rich large B cell lymphoma (THRLBCL) is a rare variant of diffuse large B-cell lymphoma (DLBCL; see this term), mainly affecting middle-aged men and often not being discovered until an advanced disease stage, with involvement of the spleen, liver and bone marrow occurring at a greater frequency than in DLBCL. It is often difficult to diagnose due to its similarity with other lymphoid diseases such as classic Hodgkin lymphoma and nodular lymphocyte-predominant Hodgkin lymphoma (see these terms) and has an aggressive clinical course.