SOX11 is useful in differentiating cyclin D1-positive diffuse large B-cell lymphoma from mantle cell lymphoma.

AIMS: To characterize the frequency and clinicopathological features of cyclin D1-positive diffuse large B-cell lymphoma (DLBCL) and the usefulness of SOX11 in the differential diagnosis from mantle cell lymphoma (MCL).

METHODS AND

RESULTS

We retrospectively stained 206 consecutive DLBCLs for cyclin D1, and identified three (1.5%) positive cases, comprising two in the elderly with necrosis, and a third with a starry-sky pattern. All three cases shared the same non-germinal centre B-cell (non-GCB) phenotype [CD5-/CD10-/bcl-6+/MUM1+/SOX11-], Epstein-Barr virus (EBV) negativity, and absence of CCND1 aberrations by fluorescence in-situ hybridization. The third case showed both BCL6 and MYC rearrangements: a double-hit lymphoma. In the same period there were 22 MCLs, all expressing cyclin D1, with 89% cases expressing SOX11, a frequency that is statistically different from cyclin D1-positive DLBCL. Notably, we identified a pleomorphic MCL initially misdiagnosed as DLBCL. A separate cohort of 98 DLBCL cases was negative for SOX11, with only one case expressing cyclin D1 with a GCB phenotype (CD10+/bcl-6+/MUM1-). The two patients with tumour necrosis rapidly died of disease. The other two were in complete remission after immunochemotherapy.

CONCLUSION

Cyclin D1-positive DLBCLs are rare, and they are negative for SOX11 or CCND1 aberration. SOX11 is useful in differentiating cyclin D1-positive DLBCL from MCL.