Myeloid sarcoma is a tumor mass of immature myeloid or granulocytic cells that affects extramedullary anatomic sites, including uncommonly the oral cavity. A 24-year-old female was referred for evaluation of a fast growing painful gingival swelling lasting 2 weeks, associated with fever, fatigue, and cervical lymphadenopathy. Intraoral examination showed a bluish swelling on the right posterior lower gingiva exhibiting necrotic surface. Incisional biopsy of the gingival lesion displayed diffuse infiltration of undifferentiated tumor cells with granulocytic appearance, strongly immunopositive for CD99, myeloperoxidase and Ki-67 (60%), and negative for CD20, CD3, CD34 and TdT. Blood tests presented a severe pancytopenia, and genetic analysis confirmed the diagnosis of acute promyelocytic leukemia. The final diagnosis was of oral myeloid sarcoma associated with acute promyelocytic leukemia with t(15;17). The patient was submitted to chemotherapy but died of the disease one month later. The clinicopathologic and immunohistochemical features of the present case are compared with the 89 cases of oral myeloid sarcoma previously reported in the English-language literature.