An Unusual Cause of Epistaxis: Paranasal Sinus Myeloid Sarcoma.

We report a case of a 65-year-old female who presented with right-sided headaches, blurring of vision in the right eye, cold-induced epistaxis, and facial numbness in the trigeminal nerve distribution. Laboratory studies revealed a significant number of myeloblasts on peripheral smear with granulated cytoplasm, irregular nuclei, and prominent vacuoles. Magnetic resonance imaging (MRI) of the brain demonstrated a T1-enhancing 1.5 cm right-sided dural-based lesion involving the medial sphenoid wing, cavernous sinus, infratemporal fossa, and sphenoid sinus region. An endoscopic biopsy of the lesion within the sphenoid sinus confirmed the diagnosis of myeloid sarcoma, with myeloblasts comprising 30% of cellularity by flow cytometry. A subsequent bone marrow biopsy revealed a hypercellular marrow with 23% blasts by flow cytometry that demonstrated a similar immunophenotypic pattern to those seen in the sinus mass. Fluorescence in situ hybridization (FISH) testing revealed the balanced translocation t(8;21)(q22;q22.1), consistent with a diagnosis of acute myeloid leukemia with RUNX1-RUNX1T1-balanced translocation by WHO 2016 criteria. Myeloid sarcoma represents a rare extramedullary presentation of acute myeloid leukemia (AML), either alone or in conjunction with blood or bone marrow involvement. This case emphasizes the need for a broad differential diagnosis and an aggressive work-up for any unusual paranasal sinus mass.