Contribution of Flow Cytometry to the Diagnosis of Malignant and Non Malignant Conditions in Lymph Node Biopsies

In order to assess the contribution of FC to the diagnosis of lymph node disorders we retrospectively compared the pathological and the FC diagnosis made in 118 consecutive lymph node biopsies. Pathological diagnosis included non malignant conditions (n = 43), B-cell Non Hodgkin lymphoma (NHL) (n = 30), T-cell NHL (1 case), carcinoma (n = 18), Hodgkin lymphoma (HL) (n = 15), melanoma (n = 2), chronic myelocytic leukemia (n = 12), miscellaneous non-lymphoid tissues (n =6 ) and undetermined conditions (n = 2). Among the 116 assessable samples, FC was in agreement with histology in 102 cases (87.9%; 95%CI = 81 – 93) which included 38 benign conditions (90%; 95% CI = 77 – 97%), 29 NHL (96.7%; 95% CI = 83 – 100), 18 carcinomas (100%; 95% CI = 81 – 100), and 12 HL (80.0%; 95% CI = 52 – 96). Discrepancies (14 cases) included 3 HL undiagnosed by FC and 2 granulomatous adenitis with an erroneous FC diagnosis of HL. Finally, a malignant condition was suspected only by FC in 5 cases (1 carcinoma, 2 B-cell and 2 T-cell NHL) and subsequently demonstrated by additional diagnostic procedures. In conclusion, this study confirms that FC performed on fresh lymph node samples is a powerful diagnostic tool in patients with malignant lymphoma. A few cases left undiagnosed by classical pathological analysis can be recognized by FC. Carcinoma is readily identified by FC analysis, while some benign conditions and Hodgkin lymphoma can be misdiagnosed with the use of FC, although the potential of FC to properly recognize HL is improving compared to previously reported studies. FC is a useful adjunct to pathological analysis of lymph node specimens.