The most frequent type of lymphoblastic lymphoma. It comprises approximately 85-90% of cases. It is more frequently seen in adolescent males. It frequently presents with a mass lesion in the mediastinum. Pleural effusions are common. (WHO, 2001). The disease is Monarch Disease Ontology entry MONDO_0044917 (T-lymphoblastic lymphoma). Also known as: Precur. T-lymphoblastic lymphoma, T Lymphoblastic lymphoma, T-Lymphoblastic lymphoma, precursor T Lymphoblastic lymphoma, precursor T-Lymphoblastic lymphoma, precursor T-cell Lymphoblastic lymphoma, precursor T-lymphoblastic lymphoma.