Acute monocytic leukemia with t(8;22)(p11;q11)/BCR::FGFR1, trisomy 8, and concurrent RUNX1/STAG2 mutations: A rare case report and literature review.

INTRODUCTION

Myeloid neoplasms harboring t(8;22)(p11;q11)/BCR::FGFR1 rearrangement are exceptionally rare and are typically associated with aggressive clinical behavior. The coexistence of trisomy 8 with concurrent RUNX1 and STAG2 mutations in this cytogenetic context has not been systematically described.

CASE PRESENTATION: We report a 71-year-old female who presented with fever, dysuria, cough, shortness of breath, and melaena. Initial laboratory evaluation revealed anemia, leukocytosis, and severe thrombocytopenia, with approximately 60% peripheral circulating blasts. Bone marrow examination demonstrated 78% blasts with monocytic morphology. Flow cytometry identified an abnormal blast population (∼87% of viable events) expressing CD33 and CD64 with variable CD13, CD38, HLA-DR, CD11c, and CD15, and a small subset positive for cytoplasmic myeloperoxidase, consistent with acute monocytic leukemia. Conventional cytogenetics revealed 47,XX,+8,t(8;22)(p11;q11). Targeted next-generation sequencing detected a BCR::FGFR1 fusion along with a likely pathogenic RUNX1 missense mutation affecting the Runt homology domain and a loss-of-function STAG2 frameshift mutation. The patient was treated with azacitidine and venetoclax, achieving early hematologic response with clearance of circulating blasts.

CONCLUSION

This case highlights a rare presentation of acute monocytic leukemia with trisomy 8 and t(8;22)(p11;q11)/BCR::FGFR1 rearrangement harboring concurrent RUNX1 and STAG2 mutations. These findings expand the molecular spectrum of FGFR1-rearranged neoplasms and underscore the value of integrated cytogenetic and molecular diagnostics in defining uncommon AML presentations.