Monoclonal B-Cell Lymphocytosis

**Semantic type:** Neoplastic Process

**Definition:** A monoclonal expansion of B-lymphocytes with or without the characteristic immunophenotype of chronic lymphocytic leukemia. It precedes virtually all cases of chronic lymphocytic leukemia/small lymphocytic lymphoma.

**Synonyms:** - MBL - MBL - monoclonal B-cell lymphocytosis