Quantitative image analysis in the assessment of diffuse large B-cell lymphoma.

Proliferation rates in diffuse large B-cell lymphoma have been associated with conflicting outcomes in the literature, more often with high proliferation associated with poor prognosis. In most studies, the proliferation rate was estimated by a pathologist using an immunohistochemical stain for the monoclonal antibody Ki-67. We hypothesized that a quantitative image analysis algorithm would give a more accurate estimate of the proliferation rate, leading to better associations with survival. In all, 84 cases of diffuse large B-cell lymphoma were selected according to the World Health Organization criteria. Ki-67 percentage positivity estimated by the pathologist was recorded from the original report. The same slides were then scanned using an Aperio ImageScope, and Ki-67 percentage positivity was calculated using a computer-based quantitative immunohistochemistry nuclear algorithm. In addition, chart review was performed and survival time was recorded. The Ki-67 percentage estimated by the pathologist from the original report versus quantitative image analysis was significantly correlated (P<0.001), but pathologist Ki-67 percentages were significantly higher than quantitative image analysis (P=0.021). There was less agreement at lower Ki-67 percentages. Comparison of Ki-67 percentage positivity versus survival did not show significant association either with pathologist estimate or quantitative image analysis. However, although not significant, there was a trend of worse survival at higher proliferation rates detected by the pathologist but not by quantitative image analysis. Interestingly, our data suggest that the Ki-67 percentage positivity as assessed by the pathologist may be more closely associated with survival outcome than that identified by quantitative image analysis. This may indicate that pathologists are better at selecting appropriate areas of the slide. More cases are needed to assess whether this finding would be statistically significant. Due to the good correlation between pathologist estimate and quantitative image analysis, there is no substantial benefit to using quantitative image analysis at this point of time.

Bone marrow examination for unexplained cytopenias reveals nonspecific findings in patients with collagen vascular disease.

CONTEXT: Collagen vascular diseases are frequently included in the differential diagnosis for unexplained cytopenias and often prompt a bone marrow biopsy in this patient population to exclude malignancy. Few large-scale studies have characterized the bone marrow morphology in patients with collagen vascular disease, and most are limited to systemic lupus erythematosus or rheumatoid arthritis. OBJECTIVE: To identify morphologic and immunohistochemical abnormalities specific to each of a wide range of collagen vascular disease cases. DESIGN: We examined 102 cases of collagen vascular disease and 38 controls and evaluated the complete blood count, peripheral blood morphology, bone marrow morphology, as well as immunohistochemical staining, for numerous cell lineages. RESULTS: Bone marrow findings, including abnormalities such as lymphoid aggregates, lipogranulomas, or abnormal localization of immature precursors, were not significantly different as compared to the control group. CONCLUSIONS: Bone marrow examination in patients with collagen vascular disease with cytopenias seldom provides new information. Caution should be exercised in interpreting morphologic findings suggestive of myelodysplasia since these are of a reactive nature in up to 27% of patients with collagen vascular disease. In a cost-effective diagnostic strategy, successful utilization may favor postponing a bone marrow biopsy while a more standardized autoimmune diagnostic panel is being performed.

Translocations involving MUM1 are rare in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) comprises a diverse group of neoplasms that have recently been subdivided by gene expression profiling and immunohistochemical studies into at least 2 subgroups [germinal center (GC) type and non-GC type]. The non-GC subtype has a post-GC activated phenotype and typically expresses MUM1 by immunohistochemistry. We hypothesized that MUM1 may be dysregulated/up-regulated in these tumors by a chromosomal translocation, as is seen in many cases of plasma cell myeloma [where MUM1 is juxtaposed with the immunoglobulin heavy chain gene (IgH)]. Therefore, using a novel MUM1 break-apart probe constructed in our laboratory, we performed fluorescence in situ hybridization on 33 cases of DLBCL (17 GC type and 16 non-GC type) for a MUM1 translocation. We identified 1 case of a MUM1 translocation out of 31 cases with successful fluorescence in situ hybridization. This case was a non-GC DLBCL (1/15). We conclude that genetic abnormalities involving MUM1 are rare in DLBCL and that a mechanism of deregulation of the MUM1 protein other than by a translocation event is involved in the majority of non-GC cases.

Most morphologic features in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) do not reliably predict underlying FISH genetics or immunoglobulin heavy chain variable region somatic mutational status.

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is common in the Western world. Genetic abnormalities detected by fluorescence in situ hybridization (FISH) and immunoglobulin heavy chain variable gene region (IGHV) mutational status are well-known independent prognostic indicators in CLL/SLL. Given the requirement for specialized testing to detect such aberrations, we investigated whether morphologic features may predict the presence of a more or less favorable genetic profile. Forty-one SLL cases were morphologically evaluated for expanded proliferation centers, increased large cells outside of proliferation centers, and nuclear contour irregularities (NCI) in small and large tumor cells. ZAP-70 immunohistochemistry and FISH (deletions of 13q14, p53 and ATM and trisomy 12) were successful in all cases. IGHV mutational status was determined in 26/41 cases. Significant NCI in both small and large cells correlated with the presence of an unfavorable FISH abnormality (ie, ATM or p53 deletions). However, despite good specificity (94%), the sensitivity (57%) of this finding is inadequate for routine use. No other significant associations with morphologic features were identified. Strong ZAP-70 positivity correlated with unmutated IGHV (P=0.001), rendering ZAP-70 IHC a useful surrogate for IGHV mutational status. ZAP-70 positivity predicted against finding a favorable FISH deletion 13q14 (P=0.023). Although we only studied 41 cases, we corroborated their validity using Kaplan-Meier overall survival analysis. In conclusion, morphologic features in SLL are not a reliable predictor of underlying genetic status. Thus, we propose a practical, cost-effective approach to the work-up of these cases, which should be driven by clinical necessity.

Diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma is the most common lymphoma worldwide. Both morphologically and prognostically it represents a diverse spectrum of disease. Traditional morphologic subclassification often results in poor interobserver reproducibility and has not been particularly helpful in predicting outcome. Recent gene expression profiling studies have classified diffuse large B-cell lymphoma into 2 main subtypes, germinal center B-cell and activated B-cell, with the germinal center type showing an overall better survival. Validation of these subtypes has become possible for the practicing pathologist with the use of surrogate immunohistochemical markers. Importantly however, these prognostic studies were performed on material from the pre-rituximab treatment era. With the now well-accepted addition of rituximab (anti-CD20 antibody) to the typical large B-cell lymphoma chemotherapeutic regimen, a revalidation of any survival differences between the large B-cell lymphoma subgroups is necessary. This short review covers the current clinical, morphologic, immunophenotypic, genetic, gene expression profiling, and prognostic (studies before and after the addition of rituximab) features of de novo diffuse large B-cell lymphoma.