Morphologic characteristics of MMR deficient tumors include an expanding tumor growth pattern, poor and mucinous differentiation, a solid/medullary growth pattern, lack of “dirty necrosis” and lymphocytic reactions such as peritumoral lymphocyte infiltration, Crohn-like reactions and presence of tumor-infiltrating lymphocytes (TIL) [6,8-10]. The gene discussed is MRC1; the disease is neoplasm.