A 60-year-old man is found to have a 5-cm exophytic mass in the ascending colon during a screening colonoscopy. Biopsy of the mass shows adenocarcinoma. The patient has no personal or family history of malignancy or colonic polyps. His medical problems include hypertension, and he does not use tobacco or alcohol. CT scan of the chest and abdomen reveals no metastatic lesions in the lungs or liver. A right colectomy is performed. The presence of which of the following indicates a poor prognosis in this patient?

Question

A 60-year-old man is found to have a 5-cm exophytic mass in the ascending colon during a screening colonoscopy.  Biopsy of the mass shows adenocarcinoma.  The patient has no personal or family history of malignancy or colonic polyps.  His medical problems include hypertension, and he does not use tobacco or alcohol.  CT scan of the chest and abdomen reveals no metastatic lesions in the lungs or liver.  A right colectomy is performed.  The presence of which of the following indicates a poor prognosis in this patient?

Quizplus · Accepted Answer

11ec160b_393c_cdc7_9249_ffc612898df1_MD0001_00 The prognosis of colorectal cancer is most tightly correlated with tumor stage at diagnosis. Stage reflects the degree of tumor invasion and spread from the initial site of formation. Colorectal tumors confined to the basement membrane or lamina propria are considered to be carcinoma in situ and have an excellent 5-year survival rate (>90%). Invasion of the tumor into the muscularis propria, the location of the colonic lymphatic channels, is associated with a slightly worse prognosis (5-year survival rate of 70%-80%) due to elevated rates of tumor spread through lymphatics or to adjacent organs. The prognosis of colon cancer deteriorates when tumor cells are identified in regional lymph nodes (5-year survival rate of 50%-80%). Lymph node spread is thought to be one of the strongest predictors of metastatic potential and, therefore, indicates an increased risk for incurable, distant disease. Metastatic spread to distant organs (eg, lungs, liver) is associated with the worst 5-year survival rates (<15%). (Choice A) Tumor grade, the degree of cellular differentiation of tumor cells, also affects prognosis. Well-differentiated (low-grade) colonic tumors have glandular structure and are associated with a better prognosis than poorly differentiated (high-grade) colonic tumors, which appear as sheets or cords of cells with pleomorphism, high mitotic rates, and other signs of significant cellular aberration. Grade is a less important prognostic indicator than stage. (Choice B) Cytokeratin 20 is a marker of intestinal cell differentiation. Testing for the presence of this structural protein helps confirm that adenocarcinomas are of intestinal origin; it is not a prognostic indicator. (Choice C) The invasion of colorectal cancer into the lamina propria is considered to be carcinoma in situ because lymphatic channels do not arise until the subsequent layer (muscularis propria). Patients with colorectal tumors confined to the basement membrane or lamina propria have an excellent prognosis. (Choice D) Cytotoxic T-cell (lymphocytic) invasion of tumor cells is a favorable prognostic indicator as it signifies immune recognition. It is associated with a lower risk of metastases and improved survival. Educational objective: Tumor stage (degree of invasion/spread) is the most important prognostic determinant for colorectal cancer. Tumors confined to the basement membrane and lamina propria are early stage and have the best prognosis. Outcomes generally deteriorate as the stage advances: spread of tumor into the muscularis propria → regional lymph nodes → distant sites.

A 60-Year-Old Man Is Found to Have a 5-Cm Exophytic