The oncogenic role of TCL1 in chronic lymphocytic leukemia is well established in transgenic mice. TCL1 expression in other B-cell malignancies has been also described: post-germinal center-derived malignancies, such as multiple myeloma, classically do not express TCL1. Waldenström macroglobulinemia is a post-germinal center malignancy that is known to be similar to chronic lymphocytic leukemia in terms of its gene expression profile. TCL1 expression has not been so far assessed in Waldenström macroglobulinemia. Transcriptomic explorations show that TCL1A expression is linked to signaling pathways and biological functions that are known to be involved in Waldenström macroglobulinemia as well as to gene signatures of interest in B-cell malignancies. We investigated TCL1 expression at the protein level in the bone marrow of a series of 59 patients with Waldenström macroglobulinemia: 76% of patients expressed TCL1, which appeared to be associated with a pejorative prognostic impact. TCL1 could have an oncogenic role in Waldenström macroglobulinemia, and deserves further exploration.