Diagnostic and taxonomic challenges in chronic myelomonocytic leukemia with lymph node involvement: A case report and mini-review.

The WHO and ICC classifications lack standardized terminology to define the disease phase of chronic myeloproliferative neoplasms in extramedullary sites, particularly lymph nodes, when infiltrates resemble extramedullary hematopoiesis (EH). We report a lymph node case of extramedullary chronic myelomonocytic leukemia (CMML) in blast phase mimicking EH. Comprehensive genomic profiling, using chromosomal microarray and NGS-based sequencing, identified copy neutral loss of heterozygosity (cn-LOH), previously unreported in extramedullary CMML. We discuss challenges in determining the CMML disease phase in lymph nodes and review the literature to underscore the need for consensus terminology for cases not meeting myeloid sarcoma criteria.