Leukemia is a neoplastic disease with an excessive proliferation of immature white blood cells and their precursors. Common oral manifestations of acute myeloid leukemia (AML) include ulceration, petechiae, spontaneous bleeding, and gingival hyperplasia. The estimated prevalence of AML is 19 per 100,000 populations, the median age of diagnosis is over 65 years, and of all the subtypes of leukemia, AML accounts for the highest percentage of leukemic deaths. The purpose of this study is to report the case of a 77-year-old female patient, who visited our outpatient clinic due to consistent inflammatory findings. Though she received surgical treatment, she was diagnosed with AML by chance after a preoperative blood test. We also discuss the necessity of performing a preoperative blood test prior to invasive dental procedures such as tooth extraction or biopsy.