I A. Precursor B-cell neoplasms 1. Precursor B-cell leukemia/lymphoma IA. Precursor T-cell neoplasms Precursor T-cell leukemia/lymphoma pre-B-lymphoblastic tumor: first leukemia lymphoma pre-T-lymphoblastic tumor: mediastinal masses involved the thymus leukemia Both tumors usually have the clinical appearance of an acute lymphoblastic leukemia (ALL)ⅠA. Precursor B-cell neoplasms 1. Precursor B-cell leukemia/lymphoma ⅡA. Precursor T-cell neoplasms 1. Precursor T-cell leukemia/lymphoma pre-B-lymphoblastic tumor: first leukemia lymphoma pre-T-lymphoblastic tumor: mediastinal masses involved the thymus leukemia Both tumors usually have the clinical appearance of an acute lymphoblastic leukemia (ALL)