A precursor T-cell, called a T-cell lymphoblast, is an immature lymphocyte that is eventually destined to become a mature T-cell. It is this cell that becomes cancerous in precursor T-cell lymphoblastic lymphoma.
Precursor T-cell lymphoblastic lymphoma is a type of aggressive NHL that occurs mainly in children and adolescents, and more often in males than females. A second peak of occurrence is seen later in life in people over 40 years of age.