Fine-needle aspiration cytology in the diagnosis of lymphoma. The next step.

Since 1985, almost 200 articles have been published in the medical literature on the subject of fine-needle aspiration (FNA) cytology and the diagnosis of lymphoma. The majority of recent studies describe the usefulness of a combined approach using FNA cytology and immunophenotyping by flow cytometry (FC) or immunohistochemistry.1-12 Despite this abundance of experience, the application of FNA cytology to the diagnosis of Hodgkin lymphoma (HL) and non-Hodgkin lymphoma remains controversial.13,14 The focus of the controversy is the appropriateness of the cytologic approach for the initial diagnosis of lymphoma, rather than excisional biopsy, which is the accepted “gold standard.” In this issue of the Journal, Meda et al15 relate their 6year experience with FNA cytology of lymph nodes and extranodal sites combined with FC for the diagnosis of lymphoma using the revised European-American classification of lymphoid neoplasms.16 The authors claim a sensitivity of 95% and a specificity of 85% when diagnoses suspicious for lymphoma are considered as positive for lymphoma and a specificity of 100% for the definitive diagnosis of lymphoma. However, these high levels of diagnostic accuracy could be misleading because they were based on retrospective review and reclassification of many of the FNA specimens, and follow-up tissue biopsy specimens were available for only 110 of the 290 cytology specimens for determination of true positives and true negatives. A conservative estimate of the sensitivity of their methods for the definitive diagnosis of lymphoma using only cases with tissue confirmation is in the vicinity of 63%. These results are similar to those of Young et al10 who obtained a sensitivity of 62% for the primary diagnosis of non-Hodgkin lymphoma and 89% for previously diagnosed lymphoma. Many would argue that these results are not good enough to justify the use of this diagnostic strategy for the initial diagnosis of lymphoma. It may be helpful to tackle this debate by framing it in terms of 3 questions: Can the diagnosis of lymphoma be made on FNA cytology with FC? Should the diagnosis of lymphoma be made on FNA cytology with FC? What is gained by making the diagnosis of lymphoma by FNA cytology with FC?