Microscopic mimicry of lymphomas: diagnostic pitfalls.

A common, critical challenge for the pathologist is the distinction between lymphoma and lymphoma simulators. Ancillary studies are effective in making this distinction and should be used in descending order of their likely reliability according to the particular differential diagnostic consideration at hand. Clinical case information is essential to avoid misinterpretation. Lymphoma simulators can be grouped into several major categories: nonlymphoid neoplasms, usually high-grade, simulating high-grade lymphomas; chronic lymphoid hyperplasias simulating low-grade lymphomas; and acute lymphoid hyperplasias simulating high-grade lymphomas.