Diagnosing lymphomas that arise in immune-privileged sites of the body, such as primary vitreoretinal lymphoma (VRL) in the eye and primary central nervous system lymphoma (CNSL) in the brain, has long been one of haematology’s most difficult diagnostic challenges. These aggressive large B-cell lymphomas hide in the vitreous humour of the eye and in cerebrospinal fluid (CSF), where lymphoma cells are fragile and yields are often so paucicellular that definitive cytological diagnosis is precluded. A new study published in Experimental Hematology & Oncology reports a molecular testing workflow designed to overcome these obstacles.
Clinical testing for the MYD88 L265P mutation has been incorporated into many haematology diagnostic workflows to help identify these lymphomas when cytology falls short. However, the gel-based allele-specific PCR assays commonly used for this purpose carry important limitations. They are restricted by the amount and quality of DNA available from precious samples, they can only detect predefined hotspot variants, and they cannot detect variants in the CD79B ITAM domain, which occur in immune-privileged large B-cell lymphomas carrying the MYD88/CD79B (MCD) genotype.
To address these shortcomings, researchers developed a low-input multiplex MYD88/CD79B PCR workflow paired with Sanger sequencing. According to the study, the assay detects canonical MYD88 mutations as well as additional variants in the MYD88 TIR domain, along with mutations in the CD79B ITAM domain, broadening the molecular window far beyond the single L265P hotspot.
The clinical performance of the new workflow was evaluated in 42 vitreous specimens and 4 CSF specimens. In paired validation against clinical VRL samples and known inflammatory biopsies, a total of 46 specimens, the multiplex assay showed higher sensitivity, specificity and diagnostic accuracy over the current standard-of-care MYD88 L265P laboratory-developed test (LDT), with reported figures of 81.8 percent sensitivity, 100 percent specificity and 94.7 percent diagnostic accuracy.
A striking technical achievement was the reduction in minimum DNA input required for testing, from 1 nanogram down to 0.016 nanograms, while maintaining diagnostic concordance with the LDT, with clinical findings and with whole-exome sequencing (WES). This dramatic lowering of the DNA threshold matters greatly for samples where tumour cells are scarce and degraded, as is typical in vitreous and CSF specimens.
Beyond simply calling mutations, the workflow yielded additional biological insight. Mixed wild-type and mutant peak patterns observed in Sanger sequencing traces provided information about mutational burden and tumour heterogeneity, offering a glimpse into the clonal architecture of these lymphomas that a single-hotspot assay cannot deliver.
The authors are careful to position the new assay appropriately within the diagnostic landscape. Whole-exome sequencing remains more comprehensive in its coverage of the lymphoma genome. However, they describe multiplex MYD88/CD79B PCR with sequencing as a practical intermediate molecular strategy, one that sits between the narrow single-gene hotspot tests and the broad but resource-intensive exome approaches.
The workflow’s ability to identify the MYD88/CD79B-associated (MCD) genotype is highlighted as a key benefit, since this genotyping can support therapeutic and prognostic assessment in these rare lymphomas. Published as an open-access correspondence article on 9 October 2026, the study suggests that laboratories relying solely on MYD88 L265P testing may be missing diagnostically and clinically relevant variants in immune-privileged site lymphomas, and that broader, low-input molecular profiling could meaningfully improve molecular detection and genotyping for patients with suspected VRL or CNS lymphoma.
Subject of Research: A multiplex MYD88/CD79B PCR and Sanger sequencing workflow for detecting immune-privileged site lymphomas in vitreous and CSF samples
Article Title: Beyond MYD88-only testing: MYD88/CD79B profiling improves molecular detection and MCD genotyping in VRL and CNS lymphomas
Article References: Wang, M. M., Li, Y., How, G. F., Ho, C. E. H., Somasundaram, N. D., Chan, J. Y., Tay, T. K. Y., Hein, T., & Chan, A. S. Y. (2026). Beyond MYD88-only testing: MYD88/CD79B profiling improves molecular detection and MCD genotyping in VRL and CNS lymphomas. Experimental Hematology & Oncology, 15(1), Article 103. https://doi.org/10.1186/s40164-026-00836-7
Image Credits: AI Generated
DOI: 10.1186/s40164-026-00836-7
Keywords: primary vitreoretinal lymphoma, primary CNS lymphoma, MYD88 L265P, CD79B ITAM, MCD genotype, multiplex PCR, Sanger sequencing, laboratory-developed test, whole-exome sequencing, immune-privileged sites, molecular diagnostics, large B-cell lymphoma
News Source: Ophelia Keating. (October 28, 2026). New MYD88/CD79B Test Boosts Detection of Eye and Brain Lymphomas. Scienmag.
