Routine use of immunophenotype by flow cytometry in tissues with suspected hematological malignancies

BACKGROUND: Immunophenotype is an essential parameter in the diagnosis of hematological malignancies. Flow cytometry (FCM) is used in the analysis of bone marrow or peripheral blood samples but is less frequently used in the evaluation of tissue biopsies with suspected hematological malignancies. The aim of this study was to analyze the role of FCM in the diagnosis of biopsies from patients with a suspected hematological disorder. METHODS: A total of 422 consecutive biopsies were studied using standard morphology, immunohistochemistry (IHC), and FCM. Results of FCM were obtained in less than 3 h and were interpreted independently from morphology and IHC. RESULTS: A strong correlation between malignant disease and abnormal pattern of FCM was observed (218 of 250) with the exception of Hodgkin disease (P < 0.001). Overall, negative predictive value was 0.52 and positive predictive value was 1. Light chain restriction was observed in 182 of 201 B-cell lymphoma and in 0 of 142 non-B-cell disorders by FCM. In contrast, light chain pattern could only be evaluated in 38 of 91 cases by IHC. FCM allowed a rapid diagnosis of infrequent or high-grade malignancies such as histiocytic sarcoma or T-lymphoblastic lymphoma. The addition of FCM in the routine study of tissue biopsies facilitates the diagnosis of double pathology in five (1%) patients. CONCLUSIONS: FCM is a fast and reliable methodology for phenotyping tissue samples, which easily detects infrequent hematological malignancies, disease-specific phenotypes and clonality in B-cell lymphomas. Moreover, the simultaneous recognition of different cell populations allows the diagnosis of composite cell lymphomas, or double pathologies.