Bone marrow staging of patients with non-Hodgkin lymphoma by flow cytometry - Correlation with morphology

BACKGROUND. Immunophenotypic analysis is an established tool in the diagnos is and classification of many hematolymphoid disorders; however, the role o f flow cytometry (FC) in detecting bone marrow involvement during the stagi ng of non-Hodgkin lymphoma (NHL) has yet to be defined. METHODS. The authors retrospectively analyzed 157 staging and 70 restaging bone marrow biopsies on which morphologic and FC analyses were performed; t hese biopsies were taken from 195 consecutive patients. Bone marrow biopsie s were blindly and independently reviewed and determined to be positive, ne gative, or suspicious for morphologic involvement by NHL, with disagreement s settled by a third reviewer. A selected panel of monoclonal antibodies wa s used to determine whether bone marrow involvement was immunophenotypicall y positive (>5%), minimal (<5%), negative, or nondiagnostic. RESULTS. FC and morphology agreed in 78% of cases (178 of 227: 129 both neg ative, 49 both positive) and were discrepant in 22% (49 of 227). Seven perc ent (16 of 227) were morphologically positive but showed no evidence of dis ease on FC, whereas 12% (27 of 227) were positive by FC but had no morpholo gic involvement, Of the 162 morphologically negative or suspicious bone mar rows, 27 were shown to be involved by FC, resulting in a false-negative det ection rate of 17%. Most of these (22 of 27, 81%) had minimal detectable di sease. Seven percent of Stage I and 26% of Stage II NHL cases with negative staging bone marrow morphologically were found to be involved by FC. CONCLUSIONS. Neither morphologic examination of bone marrow biopsy specimen s nor FC alone is adequate to detect all cases of NI-IL with bone marrow in volvement. FC is most sensitive for detecting minimal bone marrow lymphoma, whereas morphology will detect most cases in which involvement is >5%. Cas es of early stage NHL with morphologically negative bone marrow could poten tially be restaged as Stage TV on the basis of FC results. The clinical imp ortance of minimal bone marrow involvement by NHL needs further evaluation. (C) 2000 American Cancer Society.