Lymph Nodes Triaging by General Surgical Pathologists – Flow Cytometry or Immunohistochemistry or Both?

Abstract

Abstract Introduction/Objective The diagnosis of lymphoma has become complex due to existing WHO/ICC classifications. Triaging Lymph Nodes (LN) is an important first step in making the correct and precise diagnosis in a timely and cost- effective manner, initiating appropriate treatment and predicting prognosis. Surgical Pathologists (SPs) face challenges when it comes to triaging LNs for Flow Cytometry (FC) and Immunohistochemistry (IHC), as limited guidelines are available for triaging and every practice doesn’t have hematopathologist (HP) on site. Methods/Case Report We retrospectively evaluated 850 LNs (excision, core or FNAs) during 2009-2022; and divided samples into two groups (without additional esoteric testing) that were blinded from each other: Group I: FC and morphology (460) and Group 2: IHC and morphology (390). Diagnostic categories (DC) were 1) Reactive (RE-140); 2) B-cell lymphomas (BLy-375); 3) T-cell lymphomas (TLy-75); 4) Hodgkin Lymphomas (HL-230) & 5) Non-heme malignancy (NHM-30). Results (if a Case Study enter NA) Group I – Diagnosis was made independently in 5 DCs as follows: RE (90%); BLy (45%); TLy (10%); HL (10%) and NHM (20%). Group II – Diagnosis was made independently in 5 DCs as follows: RE (70%); Bly (80%); TLy (70%); HL (90%) and NHM (100%). Conclusion We concluded that touch imprints or cytological preparation are important steps when triaging LNs and summarize our findings as follows: 1) Combination of both FC and IHC are useful when triaging LNs; 2) FC overall results in cost savings; 3) FC is a powerful tool to be used for initial work-up and guiding further IHC work-up and diagnosis can be rendered faster when FC data is available; 4) FC is more valuable in RE and low grade BLy, while IHC in high grade BLy; 5) IHC is more valuable in TLy, HL and NHM. Therefore, it is imperative for pathology practices to prioritize the triaging of LNs initially for FC followed by IHC as needed.