Myeloid/Lymphoid Neoplasm with FGFR1::ZMYM2 Rearrangement Presenting as T-Cell Acute Lymphoblastic Lymphoma with...

Background: Myeloid/lymphoid neoplasms with FGFR1 rearrangement (MLN-FGFR1), also known as 8p11 myeloproliferative syndrome, are rare and aggressive hematologic malignancies arising from pluripotent stem cells. The FGFR1::ZMYM2 fusion resulting from t(8;13)(p11.2;q12) characteristically co presents as T-lymphoblastic lymphoma in lymph nodes alongside a myeloproliferative neoplasm in the bone marrow. The disease is resistant to tyrosine kinase inhibitors and conventional chemotherapy, and carries a median survival of less than 12 months without allogeneic hematopoietic stem cell transplantation (allo-HSCT). Case Presentation: We report a 23-year-old female who presented with progressive cervical lymphadenopathy and hyperleukocytosis (WBC 186.6 K/μL). Excisional lymph node biopsy demonstrated T-cell acute lymphoblastic lymphoma (T-ALL) with eosinophilic infiltration; immunohistochemistry confirmed lymphoblasts positive for CD1a, CD2, CD3, CD4, CD5, CD7, CD8, and TdT. Concurrent bone marrow biopsy showed a myeloproliferative neoplasm without excess blasts. Chromosomal analysis confirmed t(8;13)(p11.2;q12) with FGFR1::ZMYM2 rearrangement, and NGS identified a concurrent CSF3R variant (Q741*). She received induction chemotherapy per the PEDS AALL1231 protocol (Arm A) followed by consolidation, with a course complicated by hyperleukocytosis, venous thromboembolism, E. coli bacteremia, and severe mucositis requiring PICU admission. Despite initial response, the disease progressed to acute myeloid leukemia (AML) with acquisition of a PTEN variant; the patient was offered but did not complete allo-HSCT and died of refractory AML approximately 10 months after diagnosis. Conclusions: This case highlights the aggressive clinical course and diagnostic challenges of MLN-FGFR1, a rare stem cell-derived myeloid/lymphoid neoplasm. To our knowledge, this appears to be the first reported case documenting sequential CSF3R and PTEN variant acquisition with complete follow-up through fatal AML transformation, and the first to describe treatment with a pediatric ALL induction protocol (PEDS AALL1231) in this setting. The characteristic histomorphologic pattern of eosinophil-rich T-ALL in lymph nodes with concurrent myeloproliferative neoplasm in bone marrow should prompt immediate molecular workup. Allo-HSCT must be pursued urgently at diagnosis, as complications rapidly narrow the transplant window and the disease is uniformly fatal without it.