Fine-needle aspiration (FNA) became important for the cytology of the enlarged lymph node in the 1950s and 1960s and was accepted in the diagnosis of various types of lymphadenitis and metastatic disease. The diagnosis of lymphoma by FNA cytology, however, remained controversial for many years, as FNA smears did not allow the evaluation of growth pattern. Only later with the introduction of immunocytochemistry on FNA material it became possible to conclusively diagnose the majority of lymphomas with an accuracy comparable to that of histopathology. Other ancillary techniques such as FISH and PCR can now also be applied successfully to FNA material. These facts together with the excellent clinical performance of FNA sampling should increase the spread of the technique. This comprehensive manual presents the cytomorphologic and immunocytochemical characteristics of both non-Hodgkin and Hodgkin lymphomas. It discusses the technical, methodological aspects of lymphoma diagnosis and describes the cytologic features of reactive lymphoid lesions and the major types of neoplastic lymphoid lesions, based on the most recent (2001) WHO lymphoma classification. Key cytologic and immunologic features are listed to facilitate a conclusive diagnosis of the different lesions. This publication will be of immense value to clinicians such as cytopathologists, pathologists, oncologists, and hematologists involved in the clinical work-up and management of patients with lymph node lesions.