This assumes even more relevance if we consider that a similar situation of ATM biallelic loss and TCL1 overexpression, other than in AT patients, exists also in several sporadic human cancer types, such as T-PLL, B-CLL and mantle cell lymphoma, suggesting that these two genes cooperate in the development of certain lymphoid tumours. Here, TCL1B is linked to B-cell chronic lymphocytic leukemia.