Recurrent Chromosomal Abnormalities in Tissues Involved by Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma

Assessment for acceleration and transformation of chronic lymphocytic leukemia/small lymphocytic lymphoma using histologic and immunohistochemical features: a case series

Morphologic features of aggressive/ "accelerated" chronic lymphocytic leukemia/small lymphocytic lymphoma (aCLL/SLL) have been described. Richter transformation (RT) also occurs in a subset of CLL/SLL cases. This case series examined inter-observer variability when assessing for aCLL/SLL and RT, with attention to how immunohistochemical (IHC) markers may assist in this evaluation. Twelve cases of CLL/SLL with available FFPE tissue were identified. H&E staining and IHC (CD3, CD20, CD5, CD23, LEF1, LAG3, C-MYC, PD-1, MUM1, Cyclin D1, BCL-6, p53, and Ki-67) were performed. Three hematopathologists reviewed each case. The pathologists provided a final interpretation of (1) CLL/SLL, (2) CLL/SLL with expanded and/or confluent proliferation centers or increased Ki-67 (aCLL/SLL), or (3) large cell transformation/DLBCL. The pathologists lacked consensus in the diagnosis in 6/12 cases (50%). The reviewers disagreed on the presence of expanded/confluent proliferation centers in 8/12 cases (67%). With the exception of Ki-67, no IHC marker showed a difference in the staining profile in aCLL/SLL or RT compared to low-grade cases. This series showed inter-observer variability in the evaluation for aCLL/SLL and RT. A study that serially examines genetic alterations in FFPE tissue and correlates the features with histology and IHC, at diagnosis and throughout the disease course, may help refine indicators of aggressive disease.

Methodological and conceptual challenges to the flow cytometric classification of leukemic lymphoproliferative disorders

The diagnosis of leukemic B-cell lymphoproliferative disorders (B-LPDs) is made by integrating clinical, cytological, cytometric, cytogenetic, and molecular data. This leaves room for differences and inconsistencies between experts. In this study, we examine methodological and conceptual aspects of the flow cytometric classification of leukemic B-LPDs that could explain them. Among methodological aspects, we discuss (1) the different statistical tests used to select and evaluate markers, (2) how these markers are analyzed, (3) how scores are interpreted, (4) different degrees to which diagnostic information is used, and (5) and the impact of differences in study populations. Among conceptual aspects, we discuss (1) challenges to integrating different biological data points, (2) the under examination of the costs of misclassification (false positives and false negatives), and finally, (3) we delve into the impact of the lack of a true diagnostic gold standard and the indirect evidence suggesting poor reproducibility in the diagnosis of leukemic B-LPDs. We then outline current harmonization efforts and our personal approach. We conclude that numerous flow cytometry scores and diagnostic systems are now available; however, as long as the considerations discussed remain unaddressed, external reproducibility and interobserver agreement will not be achieved, and the field will not be able to move forward if a true gold standard is not found.