Best Practice No 185. Cytological and molecular diagnosis of lymphoma.

With the advances in molecular pathology, the cell as a morphological and functional unit has become essential in the diagnosis of lymphoma. Conventional staining, preparation, and interpretation of cells, as seen in fine needle aspiration cytology (FNAC), often used as a first line investigation of lymphadenopathy, is being supplemented with an array of immunocytochemical and molecular analyses, aimed not only at a more precise disease definition, but also at recognising factors that can predict prognosis and response to treatment. Accepting the pitfalls of conventional cytomorphology, this review looks at molecular changes characteristic to particular lymphomas and explores the currently available technology for their detection, with particular reference to cytological material. Future protocols for the diagnosis and management of patients with lymphadenopathy should include FNAC as an initial investigation, followed by immunocytochemistry and molecular investigations. Tissue biopsy, the conventional method of diagnosis, may be avoided in selected cases.