We present case of oral and skin anaplastic T-cell lymphoma in a 68-year-old woman. The patient presented with extensive ulcerations and necrotic tissue on the left mandibular gingiva. Orthopantomogram finding showed extensive necrolytic lesions of the adjacent mandible. Biopsy finding of oral lesions and subsequently of the skin confirmed the diagnosis of anaplastic T-cell lymphoma. The bridge on the teeth 35-37 was taken out. After three cycles of chemotherapy, oral lesions subsided, unlike skin lesions. Dentists should be aware that differential diagnosis when dealing with oral ulcerations might be the result of certain malignant hematologic diseases.