To demonstrate that aromatase inhibition indeed stimulates lymphoma growth and that it is not specific for Letrozole, or that the effect on lymphoma growth is not restricted to the murine T cell lymphoma EG7 but also affects human B cell lymphoma and, finally, is not dependent on an intact immune system, we grafted immune deficient NSG mice with human lymphoma B cells (Granta-519). This evidence concerns the gene CYP19A1 and B-cell non-Hodgkin lymphoma.