W ith the exception of a few countries, the renaissance of the fine-needle (thin) aspiration biopsy (FNAB) technique as a tool with which to issue a pathologic diagnosis via a cytologic rather than a histologic preparation has occurred worldwide only within the past 30 years. Mass lesions of the thyroid gland, breast, and salivary gland have been the major clinical targets of this form of pathologic diagnosis. FNAB of the lymph nodes has been applied successfully and embraced clinically in many hospitals and clinics as an accurate and efficacious method to diagnose reactive lymphoid hyperplasia, infectious lymphadenitis, and metastatic tumors (primarily carcinomas). However, when applied to the diagnosis of malignant lymphoma (ML), particularly a primary diagnosis of malignant lymphoma in a new patient, opinion is markedly divided among pathologists as well as between pathologists and clinicians. At times, this debate appears to have little room for compromise.
Several editorials have been written just within this decade advocating both for 1-3 and against 4 the application of this diagnostic modality to ML. The reasons for viewing FNAB diagnosis of ML either with great enthusiasm or with skepticism and disdain are varied, but two major barriers preventing the success of ML diagnosis by FNAB are sampling error and ML classification. Success in FNAB is extremely operator-dependent. In those medical centers in which the training, experience, interest, attention to detail, and enthusiasm for applying FNAB to lymph nodes are absent, the quality of the sample and the resulting diagnostic accuracy will reflect this apathy. The converse applies to those laboratories in which the attitude toward FNAB is exactly the opposite. The other major impediment to ML diagnosis by FNAB cytopathology was the existence of various classifications for this group of tumors. The major classification used in this country during the past 17 years (the Working Formulation) is based to a large degree on the ability of the pathologist to evaluate the follicular or diffuse architecture of the lymphocytic proliferation within tissue, a parameter that cannot be assessed using FNAB. This latter circumstance is undergoing a radical transformation. A new World Health Organization (WHO) histologic classification for hematologic malignancies currently is under development. It is based heavily on the principles of the previously published Revised European-American Classification of Lymphoid Neoplasms (REAL) classification system, which encompasses not only the morphologic and 322 CANCER CYTOPATHOLOGY