A 59 male presented to emergency room with severe headache and blurry vision. Head CT scan revealed trace bilateral frontal and left parietal subarachnoid hemorrhage. He has a known history of acute promyelocytic leukemia and currently is not on leukemia treatment.

CSF cytology showed numerous abnormal promyelocytes with prominent cytoplasmic primary granules, some of these cells exhibit butterfly-shaped or bilobed nuclei (Wright-Giemsa stain, panel A; original magnification ×200, panel B; original magnification ×1000). By flow cytometry analysis, the leukemic cells were positive for CD117, CD13, CD33, CD38, CD64, and CD2 (partial), while negative for CD34, HLA-DR, CD10, CD14, CD16, CD19, CD20, and CD11c.  Fluorescence in situ hybridization (FISH) study revealed positive PML::RARA gene rearrangement and confirmed the diagnosis.