A slow-growing type of leukemia (blood cancer) in which too many lymphocytes are found in the bone marrow and/or blood. The T-cell is specified as the defective cell line. The disease is T-cell prolymphocytic leukemia (Monarch Disease Ontology id MONDO_0019468). Also known as: CLL, T-cell, T cell CLL, T cell chronic lymphocytic leukaemia, T cell chronic lymphocytic leukemia, T cell prolymphocytic leukaemia, T cell prolymphocytic leukemia, T prolymphocytic leukaemia, T prolymphocytic leukemia.