Establishing the diagnosis of lymphoma: from initial biopsy to clinical staging.

Successful therapy for most of the non-Hodgkin's lymphomas requires an accurate pathologic diagnosis. Routine morphologic examination of excisional biopsies from nodal or extranodal sites provides the cornerstone for establishing a definitive diagnosis. The list of ancillary studies, however, used to complement these routine approaches is increasing both in number and complexity. Proper use of these diagnostic tools can be of great help in arriving at the correct diagnosis in difficult cases. Fine-needle aspiration and needle-core biopsies have a role in lymphoma staging and in the assessment of recurrent disease, but are limited as primary diagnostic tests. This review will focus on the standard approaches used to establish a diagnosis of malignant lymphoma, and the clinical utility of immunophenotypic, molecular genetic, and cytogenetic studies in providing useful data for diagnosis. The standard practice of synthesizing all of the data from multiparameter analysis to arrive at a diagnosis in difficult cases will be emphasized.