andrew field

Introduction Flow cytometry (FCM) is widely used in the diagnosis of mature B‐cell neoplasms (MBN), and FCM data are usually consistent with morphological findings. However, diffuse large B‐cell lymphoma (DLBCL), a common MBN, is sometimes not detected by FCM. This study aimed to explore factors that increase the likelihood of failure to detect DLBCL by FCM. Methods Cases with a final diagnosis of DLBCL that were analysed by eight‐colour FCM were retrospectively collated. Clinical, FCM, histopathological and genetic data were compared between cases detected and cases not detected by FCM. Results DLBCL cases from 135 different patients were analysed, of which 22 (16%) were not detected by FCM. In samples not detected by flow cytometry, lymphocytes were a lower percentage of total events ( p = 0.02), and T cells were a higher percentage of total lymphocytes ( p = 0.01). Cases with high MYC protein expression on immunohistochemistry were less likely to be missed by FCM ( p = 0.011). Detection of DLBCL was not different between germinal centre B‐cell (GCB) and non‐GCB subtypes, not significantly affected by the presence of necrosis or fibrosis, and not significantly different between biopsy specimens compared to fine‐needle aspirates, or between samples from nodal compared to extranodal tissue. Conclusion The study identifies several factors which affect the likelihood of DLBCL being missed by FCM. Even with eight‐colour analysis, FCM fails to detect numerous cases of DLBCL.

Background After a series of standardized reporting systems in cytopathology, the Sydney system was recently introduced to address the need for reproducibility and standardization in lymph node cytopathology. Since then, the risk of malignancy for the categories of the Sydney system has been explored by several studies, but no studies have yet examined the interobserver reproducibility of the Sydney system. Methods The authors assessed interobserver reproducibility of the Sydney system on 85 lymph node fine‐needle aspiration cytology cases reviewed by 15 cytopathologists from 12 institutions in eight different countries, resulting in 1275 diagnoses. In total, 186 slides stained with Diff‐Quik, Papanicolaou, and immunocytochemistry were scanned. A subset of the cases included clinical data and results from ultrasound examinations, flow cytometry immunophenotyping, and fluorescence in situ hybridization analysis. The study participants assessed the cases digitally using whole‐slide images. Results Overall, the authors observed an almost perfect agreement of cytopathologists with the ground truth (median weighted Cohen κ = 0.887; interquartile range, κ = 0.210) and moderate overall interobserver concordance (Fleiss κ = 0.476). There was substantial agreement for the inadequate and malignant categories (κ = 0.794 and κ = 0.729, respectively), moderate agreement for the benign category (κ = 0.490), and very slight agreement for the s uspicious (κ = 0.104) and atypical (κ = 0.075) categories. Conclusions The Sydney system for reporting lymph node cytopathology shows adequate interobserver concordance. Digital microscopy is an adequate means to assess lymph node cytopathology specimens.