Cell of origin in diffuse large B-cell lymphoma in systemic lupus erythematosus: molecular and clinical factors associated with survival

BACKGROUND: SLE is associated with increased risk of diffuse large B-cell lymphoma (DLBCL). DLBCL is routinely classified by cell of origin (COO), with germinal centre B-cell (GCB) being more common and indicating better prognosis in the general population. We studied COO subtyping in patients with SLE diagnosed with DLBCL and their survival. PATIENTS AND METHODS: We evaluated 20 cases of SLE with DLBCL. Immunohistochemistry analysis was performed (BCL2, MYC, BCL6, CD10, CD20, FOXP1, GCET1, MUM1) in tissue microarrays. We examined associations between molecular and clinical features, including overall survival. RESULTS: Of the 20 DLBCL SLE cases, 12/20 cases (60%) were classified as non-GCB using Hans or Choi algorithms. MYC and BCL2 protein expression was positive in 6/20 (30%) and 8/20 (40%) SLE cases, respectively, with 2/20 (10%) co-expressing both markers. Seven (7/20) had only extranodal involvement at DLBCL diagnosis. As expected, non-GCB cases had worse survival. Cases presenting exclusively with extranodal disease were associated with shorter SLE duration and better survival despite higher BCL2 protein expression. CONCLUSIONS: We present novel data characterising DLBCL in SLE. Sixty per cent of the DLBCL in patients with SLE were non-GCB. The nodal and extranodal distribution in SLE was similar to what is known in the general population, but extranodal disease occurred more often with short SLE duration and was associated with longer overall survival. More research on cancer in SLE is the key to further understanding the complex interplay between cancer and the immune system.