The general pathology

The definition of indolent lymphoma implies a lymphoid proliferation characterized, in the majority of the clinical scenarios, by a protracted, chronic course of disease, manageable over time, albeit not definitely curable. From the standpoint of the pathologist in charge of the diagnostic tissue workup, indolent grossly overlaps with so-called low grade, that is, composed of cells resembling the mature, non-blastic counterparts of the immune system, which are lymphocytes, centrocytes, plasma cells, and variants of these. This definition is formally not part of the WHO classification but still influences the diagnostic practice. A notable exception to the rule that links non-blastic morphology with indolent clinical behavior is mantle cell lymphoma, a proliferation of (mostly) small centrocytes, which presents an aggressive clinical behavior in a subset of patients. All these need to be kept in mind by both the hematologist and the pathologist when using the the “indolent” lymphoma.