50% versus 70%: is there a difference between these BCL2 cut-offs in immunohistochemistry for diffuse large B-cell lymphomas (DLBCL)?

Introduction The World Health Organization’s (WHO) update of 2017 defines the cut-off for BCL2 in immunohistochemistry (IHC) in 50% of stained cells in diffuse large B-cell lymphomas (DLBCL). The WHO’s 2017 classification, however, has no standardized value. This study analyzes associations between immunohistochemistry results for BCL2 in relation to the detection of translocations of MYC , BCL2, and BCL6 in DLBCL. Method Sixty-seven patients with DLBCL were evaluated using IHC, with CD20, CD10, BCL6, BCL2, MUM1, TDT and MYC, and fluorescence in situ hybridization (FISH) for translocations involving the BCL2 , BCL6, and MYC . Two cut-offs for BCL2 in IHC were used (50 and 70%), with the calculation of sensitivity (S), specificity (E), positive predictive value (PPV), negative predictive value (NPV), accuracy and concordance test, with a significance level of 5%. Results Using a 70% cut-off, there is a good relationship between S (88.9%, IC95% = 68.4–109.4) and E (67.2, 95% CI = 55.2–79.3), with a high NPV (97.5, 95% CI = 92.7–102.3) and statistically significant agreement (K = 0.30, p = 0.02). Using a 50% cut-off, S and NPV increase to 100%, with a specificity of 39.7% (95% CI = 27.1–52.2) and a statistically significant concordance (K = 0.15, p = 0.017). Conclusion Reduction in the percentage of immunostaining increases the detection of DLBCL with a “double-expressor” immunophenotype. The lower criterion amplifies the S and the NPV of IHC to detect translocations involving the BCL2 gene, with an impact on the diagnosis of DLBCL “double expressor”, an unfavorable prognostic group.