OBJECTIVE: To study the pathologic characteristics of bone marrow for CD5 positive small B cell lymphoma (SBL).
 METHODS: The pathologic profiles of 92 patients with CD5 positive SBL were retrospectively analyzed. The morphologic and immunophenotypic features were analyzed by flow cytometry and immunohistochemistry. IgH/CCND1 was examined by fluorescence in situ hybridization (FISH).
 RESULTS: A total of 92 patients with CD5 positive SBL were enrolled in this study, including 56 (60.9%) chronic lymphocytic leukemia /small lymphocytic lymphoma (CLL/SLL), 23 (25.0%) mantle cell lymphoma (MCL) and 13 other SBL (14.1%). Among the 13 other cases, 5, 4 and 4 cases were follicular lymphoma (FL), lymphoplasmacytic lymphoma (LPL) and splenic marginal zone lymphoma (SMZL), respectively. The frequency of patterns for bone marrow infiltration was as follow: diffuse pattern (19/92), mixed pattern (15/92), nodular pattern (9/92), interstitial pattern (8/92), and intrasinusodial pattern (2/92). All patients expressed CD19, CD20 and CD5. According to the immunophenotypic score system, all the CLL patients had 4-5 scores, while SMCL and other SBL patients had less than 3 scores. For the other SBL patients, 5 FL expressed CD10, while 3 FL, 1 LPL and 3 SMZL expressed CD23. There was a significant difference in the expression of CD23, sIgM, FMC7, CD11C and CD22 between the CLL and MCL groups (P<0.01). All 23 MCL patients expressed cyclin D1 and showed IgH/CCND1 gene translocation by FISH detection.
 CONCLUSION CD5 positive SBL includes a variety of types of lymphoma. Patterns of bone marrow for CD5 positive SBL are diversity. Immunophenotypic analysis by flow cytometry is essential in the diagnosis and differential diagnosis of CD5 positive SBL, especially for CLL.
Bone Marrow ; pathology ; CD5 Antigens ; metabolism ; Diagnosis, Differential ; Flow Cytometry ; Humans ; Immunohistochemistry ; In Situ Hybridization, Fluorescence ; Leukemia, Lymphocytic, Chronic, B-Cell ; diagnosis ; Lymphoma, B-Cell ; diagnosis ; Lymphoma, Follicular ; diagnosis ; Lymphoma, Mantle-Cell ; diagnosis ; Oncogene Proteins, Fusion ; metabolism ; Retrospective Studies ; Splenic Neoplasms ; diagnosis