Introduction: Lymphoblastic lymphoma (LBL) is a malignant neoplasm that originates from precursors of B or T lymphocytes and constitutes approximately 2% of all nonHodgkin lymphomas. They are infrequent in the oral cavity, even more so if it is an extra-nodal primary presentation. In this location, neither the clinical features nor the radiological appearance is pathognomonic and can represent significant diagnostic problems. Case Report: We present the case of a seven-year-old female patient with a slowly enlarging painless right mandibular mass of two weeks of evolution. Radiographic studies showed an infiltrative hypodense area involving the right mandibular body, compromised teeth in formation, and vestibular and lingual cortical. Histological examination revealed a malignant neoplasm with a proliferation of round, small, blue morphology cells. In addition, immunohistochemical markers for TdT and PAX5 were positive. The diagnosis was B-cell lymphoblastic lymphoma and complementary studies confirmed only mandibular involvement without infiltration to other organs. Conclusions: The presentation of this case seeks to describe a rare neoplasm in the oral cavity, including clinical and radiographic presentation, histological characteristics, and immunological profile. The importance of an early and accurate diagnosis of this entity is emphasized due to the impact on patient survival. [ABSTRACT FROM AUTHOR]