The immunostaining profile of our patient (strongly positive CK7 and positive TTF-1 with negative CDX2/CK20) supported that her rectosigmoid tumor causing near-total rectal occlusion was metastatic adenocarcinoma of lung origin, rather than primary colorectal adenocarcinoma [57–59]. The gene discussed is TTF1; the disease is colorectal adenocarcinoma.