A 50-year-old man with a history of alcohol and tobacco use presented to the dental clinic with a 1-month history of fever, nasal congestion, and an enlarging ulcer between his front teeth. Oral examination showed gingival recession, yellowing of the teeth, alveolar bone exposure, and a gap between his top two front teeth with gingival ulceration (Panel A). The ulcer had an irregular border and extended onto his hard palate (Panel B). A complete blood count was notable for lymphopenia (1000 lymphocytes per cubic millimeter; reference range, 1100 to 3200). A biopsy specimen of the ulcer was obtained. Histopathological examination confirmed the diagnosis of extranodal natural killer T-cell lymphoma (nasal type), and Epstein–Barr virus was detected on in situ hybridization. After the patient was referred to the oncology department, a positron-emission tomographic (PET) scan showed involvement of the maxillary sinuses, nasopharynx, cervical lymph nodes, upper right lung, and spleen. The patient underwent treatment with asparaginase-based chemotherapy, after which a surveillance PET scan showed disease progression. Palliative radiation therapy was recommended.