Reproducibility of SOX-11 detection in decalcified bone marrow tissue in mantle cell lymphoma patients

Mantle cell lymphoma (MCL) usually harbors the t(11;14)(q13;q32) with overexpression of CCND1 mRNA and transcription of the cyclin D1 nuclear protein. Regardless of CCND1 status, most MCLs also express the SOX11 nuclear protein, which is thus helpful in the diagnosis of the rare CCND1-negative MCLs. Recently, SOX11 has been reported to be often negative in MCLs clinically resembling marginal zone lymphoma and recently defined as "leukemic non-nodal" MCL in the incoming revision of the WHO classification of lymphoid tumors, for which the bone marrow biopsy is commonly the first diagnostic approach. Due to the less aggressive clinical behavior of the latter MCLs, the reliable determination of the SOX11 antigen in decalcified tissue is mandatory. To this end, since little data are available in the literature, four commercially available anti-SOX11 antibodies (two polyclonal and two monoclonal) were tested on 21 positive staging bone marrow (BM) biopsies from cyclin D1/SOX11-positive MCL patients (17 fixed in B5, 4 in 10% buffered formalin) and on 9 positive BM biopsies from leukemic non-nodal MCL patients. The results were compared for specificity, sensitivity, staining strength and degree of an additional staining on myeloid precursors, also evaluating possible impact of the different fixatives used. Non-mantle cell lymphomas were also tested to address specificity. All reagents showed high sensitivity but the monoclonal code CMC38221001 provided the highest specificity and the lowest degree of non-lymphoid staining on myeloid cells. Formalin fixation generally improved the performance of most antibodies when compared to B5 fixation.