IDO2 and squamous cell carcinoma: Eighty (51%) of the cases with only membranous immunostaining (which were 77–96% adenocarcinomas and 3–4% squamous cell carcinomas) presented IDO2 expression on the basolateral side of the tumor cellular membrane, with a reinforcement of the stain at the interface between tumor and stromal tissue and without an apical immunolabel (Figure 1C).