Clinical role of flow cytometry in redefining bone marrow involvement in diffuse large B-cell lymphoma (DLBCL) - A new perspective

Aims: The clinical role of flow cytometry in staging bone marrow in diffuse large B-cell lymphoma (DLBCL), especially its impact on outcome, remains uncertain. The aim was to determine the contribution of flow cytometry to conventional staging, and to study the impact of this revised staging on survival. Methods and results: One hundred and thirteen cases of DLBCL diagnosed at The Canberra Hospital from 1996 to 2005 were identified. Blinded analysis of bone marrow (BM) morphology and flow cytometric data showed involvement on morphology (M) in 25 (22.1%) cases, on flow cytometry (F) in 21 (18.6%) cases and overall (M + F) in 32 cases (28.3%); discordance was noted in 16 cases (16.1%). Cases with and without marrow involvement on conventional staging alone (M) had no significant difference in survival (P = NS). However, when BM involvement was defined as positivity on morphology and/or flow cytometry (M + F), the median survival of patients with involvement was significantly worse than patients without involvement (P = 0.026). Conclusions: Flow cytometry-positive cases should be included with those positive on morphology in a summative model to define BM involvement in DLBCL, as it may have a potential impact on predicting outcome.