Unusual Presentation of SET::NUP214-Associated Concomitant Hematological Neoplasm in a Child—Diagnostic and Treatment Struggle

Simultaneous multilineage hematologic malignancies are uncommon and associated with poorer prognosis than single-lineage leukemia or lymphoma. Here, we describe a concomitant malignant neoplasm in 4-year-old boy. The child presented massive lymphoproliferative syndrome, nasal breathing difficulties, snoring. Morphological, immunocytochemical, flow cytometry diagnostics showed coexistence of acute myeloid (AML) peripheral T-cell lymphoma (PTCL). Molecular examination revealed rare t(9;9)(q34;q34)/SET::NUP214 translocation as well common TCR clonal rearrangements both the bone marrow lymph nodes. disease primary refractoriness to lymphoid high-dose chemotherapy combined targeted therapy (trametinib + ruxolitinib). Hence, HSCT was performed, patient has since been complete remission for over year. This observation highlights importance molecular techniques determining united nature complex SET::NUP214-positive neoplasms arising from precursor cells high lineage plasticity.