MYC and lymphoma: In these mice, expression of transgenic MYC protein in T lymphoid cells is significantly higher than in B lymphoid and myeloid cells, and thymic T lymphoma is the major cause of morbidity, although these mice can also develop disseminated histiocytic myeloid (monocyte/macrophage) (Mac1+F4/80+Gr1-) tumours affecting the spleen and other organs [36].