Lymphoblastic lymphoma, seen primarily in children or young adults, is a type of non-Hodgkin lymphoma that originates from B or T lymphocyte precursors and rarely occurs in the oral cavity. A case of systemic precursor T-cell lymphoblastic lymphoma mimicking periodontitis of a lower second molar in a 20-year-old adult is currently presented. The case was initially misdiagnosed as periodontal disease and treated with tooth extraction by a dentist. Re-evaluation of the patient due to worsening of symptoms lead to cone beam computed tomography scanning that thoroughly revealed an extended osteolytic lesion of the right mandible. Afterward, a biopsy was performed, thus reaching the diagnosis of precursor T-cell lymphoblastic lymphoma. This report discusses differences in epidemiology of T-cell and B-cell lymphoblastic lymphomas, as well as their various intraoral manifestations that are mimicking a large family of oral pathology. It also focuses on conventional imaging findings that imply malignancy, which are often neglected during routine radiology interpretation.