ADA and B-cell chronic lymphocytic leukemia: Conversely, ADA activity was increased in cancerous tissue from breast [46,47,48], kidney [49], and colorectal tumours [50], in serum of patients with bladder [51] ovarian [52], laryngeal [53], and head and neck squamous cell carcinomas [54,55] and in lymphocytes of patients with chronic lymphocytic leukaemia (CLL) [56].