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Case Report: Coexistence of advanced systemic mastocytosis, chronic myelomonocytic Leukemia, and t(11;14)-positive plasma-cell neoplasm: a rare triple-clonal hematologic case

Year: 2026

Type: article

Abstract: Background SM-AHN usually coexists with myeloid disorders, whereas plasma-cell neoplasms are rare. We report a case of advanced systemic mastocytosis, CMML, and a t(11;14)-positive monoclonal plasma-cell disorder, highlighting the diagnostic challenge of overlapping clinical, biochemical, and morphologic features. Case presentation A middle-aged man presented with months of watery diarrhea, recurrent abdominal discomfort, weight loss, markedly elevated alkaline phosphatase, and persistent monocytosis. Bone marrow examination showed dense aggregates of atypical mast cells involving about 50% of marrow cellularity, with aberrant CD25 expression, and KIT D816V (variant allele frequency, 12.10%), supporting advanced systemic mastocytosis. Sustained absolute monocytosis, classical-monocyte predominance up to 98%, and mutations in TET2 , SRSF2 , and RUNX1 supported concurrent CMML-1. Marrow plasma-cell infiltration, markedly elevated lambda free light chains, a low κ/λ ratio, and t(11;14) identified a third clonal process consistent with an IgG lambda plasma-cell neoplasm. Together, these findings established coexistence of advanced SM, CMML, and a plasma-cell disorder, with early symptomatic and biochemical improvement after treatment targeting the mast-cell and myeloid components. Conclusion This case highlights the value of integrating morphology, flow cytometry, cytogenetics, and next-generation sequencing in complex hematologic presentations. The coexistence of SM, CMML, and a t(11;14)-positive plasma-cell neoplasm is exceptionally rare, with important implications for diagnosis, risk assessment, and treatment.

Source: Frontiers in Oncology

DOI: 10.3389/fonc.2026.1982665