SOX11 antibody (SRY (Sex Determining Region Y)-Box 11) is a member of the SOX family of transcription factors and is involved in the regulation of embryonic development and in the determination of cell fate (1). The diagnosis of mantle cell lymphoma (MCL) can be difficult, especially when t(11;14) translocation and cyclin D1 overexpression are not detected. In such cases, the transcription factor SOX11 represents an important diagnostic marker as it is expressed in most MCLs and, in particular, in all cyclin D1- negative MCLs reported so far (2,3). The novel mouse monoclonal SOX11-C1 antibody displays nuclear staining and offers high sensitivity and improved specificity compared to previous SOX11 antibodies in IHC based detection of MCL. In addition, flow cytometry analysis of blood and tissue samples using SOX11-C1 may allow a convenient approach to early diagnosis and follow-up of MCL patients (4). SOX11 expression has also been shown to be a favorable prognostic marker in glioblastoma (5).