Comparative analysis of immunoglobulin polymerase chain reaction and flow cytometry in fine needle aspiration biopsy differential diagnosis of non‐Hodgkin B‐cell lymphoid malignancies

Abstract

Single primer pair polymerase chain reaction (PCR) assays for the detection of clonal immunoglobulin heavy chain (IgH) gene rearrangements and immunophenotyping by flow cytometry have been proved as useful techniques in the diagnosis of lymphoid disorders in fine needle aspirates. However, a comparative analysis of both ancillary techniques in the same samples has not been previously performed. To compare the sensitivity of flow cytometry and PCR techniques, we made a wide prospective study of 77 fine needle aspiration biopsy (FNAB) samples from lymph nodes and extranodal lymphoid infiltrates. The adjunctive values of a single primer pair PCR amplification of IgH genes and of the immunophenotyping by flow cytometry were evaluated comparing their results with the final clinicopathological diagnosis of each patient supported by histological features and clinical follow up. Among the 24 B-cell non-Hodgkin lymphomas, monoclonal IgH bands were detected in 22 cases by PCR, and 21 cases were correctly considered B-cell lymphoma by flow cytometry. A monoclonal IgH band was also detected in 1 of the 53 reactive lymphoid disorders. When both ancillary techniques were combined with morphological findings, 23 of the 24 B-cell lymphomas were correctly diagnosed but one reactive lymphoid disorder was also considered a B-cell lymphoma. We demonstrate a similar level of detection of B-cell lymphomas by single round PCR and flow cytometry techniques, and a strong adjunctive value when combined with morphological findings to diagnose correctly lymphoproliferative disorders by FNAB. However, we must be cautious with PCR results since false-positive cases can occur.