Inter- and intra-observational variability in immunohistochemistry: a multicentre analysis of diffuse large B-cell lymphoma staining

AIMS

Although many immunohistochemical (IHC) cancer biomarkers have been identified, very few have translated into routine clinical practice, primarily because of technical and observational inconsistencies between studies. However, despite the obvious need to address such variability, very few studies have done so.

METHODS AND RESULTS

Using bcl-6, CD10, MUM1, GCET1 and FOXP1 antibody staining on diffuse large B-cell lymphoma cases (n = 138) as a model, we employed Cronbach α analysis to quantify interobserver and intraobserver variability between four independent observers (two per institution), scoring two tissue microarrays (TMAs) stained at both institutions using differing staining procedures. The overall concordance between all observations irrespective of staining procedure or TMA source was high (average α = 0.951), with the highest level being reached for CD10 staining (average α = 0.967) and the lowest for bcl-6 (average α = 0.924). Interslide and interinstitutional reproducibility were similarly high (average α = 0.952 and average α = 0.934, respectively). Interobserver/intrainstitutional and interobserver/interinstitutional comparisons showed lower levels of concordance (average α = 0.870 and average α = 0.877, respectively), and intraobserver/interinstitutional comparisons showed the lowest levels of concordance (average α = 0.810), particularly for bcl-6 staining (α = 0.658).

CONCLUSIONS

This study suggests that most variability in IHC studies between centres results from inherent limitations of the biomarkers investigated rather than procedural or observational differences.

BCL2 gene aberration as an IPI-independent marker for poor outcome in non-germinal-centre diffuse large B cell lymphoma

Aim:

Diffuse large B cell lymphoma (DLBCL) is the most common lymphoid malignancy in the western hemisphere, and is characterised by a highly variable outcome that impedes individual risk assessment. Lacking reliable biomarkers, the international prognostic index (IPI) has been the most reliable factor to predict survival and stratify patients for therapy. The aim of this study was to investigate the frequency and potential prognostic role of BCL2 aberrations on the chromosomal level and the protein level in a large DLBCL collective.

Methods:

Fluorescence in situ hybridisation (FISH) with commercially available dual-colour break-apart probes and immunohistochemistry were used to assess BCL2 gene abnormalities and bcl2 protein expression on validated tissue microarrays containing 224 well-characterised cases of primary DLBCL.

Results:

FISH analysis of BCL2 revealed a break in 40/215 cases (19%) and a gain in 66/171 (39%) cases. Only BCL2 gains correlated with bcl2 protein expression (p = 0.001). Presence of any BCL2 gene abnormality, particularly gains, correlated independently of the IPI with a significantly worse prognosis in DLBCL of non-germinal centre (non-GC) phenotype as opposed to DLBCL of non-GC type without this genetic alteration (p = 0.003). DLBCL of germinal centre phenotype did not show this association.

Conclusions:

Cases of DLBCL of the non-GC type with BCL2 gene aberration are accompanied by a significantly worse prognosis as opposed to cases without such gene abnormalities. It may be helpful to asses BCL2 gene abnormalities by FISH in addition to assessing established parameters for individual risk estimation in DLBCL.