Clinicopathological characteristics of follicular lymphoma with peripheral blood involvement

This study aimed to indicate patient outcomes and pathological characteristics of follicular lymphoma (FL) with peripheral blood (PB) involvement. Of 533 patients with FL, 56 (11%) had PB involvement. Of the patients treated with rituximab, 39 patients with PB involvement had significantly shorter progression-free survival than 107 patients with stage IV disease without PB involvement (p = 0.021), but the overall survival was not different (p = 0.804). The histopathology of the primary sites was usually nodal (95%) low-grade (86%) FL with IGH/BCL2 fusion (75%). Flow cytometric and immunohistochemical analyses revealed that the incidence of CD10 positivity was lower in the bone marrow (55% and 58%) and PB (41% and not available) than in the primary site (86% and 93%) (p = 0.004 and p = 0.0001, respectively). Therefore, even if small lymphoma cells in the bone marrow and PB are negative for CD10, FL cannot be ruled out.