A 65-year-old man is found to have iron deficiency anemia. He has had no cough, abdominal pain, melena, or change in bowel habits but reports anorexia and a 5-kg (11-lb) weight loss in the past 2 months. Cardiopulmonary and abdominal examinations are unremarkable. Rectal examination shows guaiac-positive brown stool. A 3-cm mass is found on colonoscopy. Biopsy shows pleomorphic cells with large, dark nuclei forming irregular, crowded glands, some of which contain mucus. Imaging studies reveal multiple mass lesions in the liver and lungs. This patient's neoplasm most likely originated from which of the following locations?

Question

A 65-year-old man is found to have iron deficiency anemia.  He has had no cough, abdominal pain, melena, or change in bowel habits but reports anorexia and a 5-kg (11-lb) weight loss in the past 2 months.  Cardiopulmonary and abdominal examinations are unremarkable.  Rectal examination shows guaiac-positive brown stool.  A 3-cm mass is found on colonoscopy.  Biopsy shows pleomorphic cells with large, dark nuclei forming irregular, crowded glands, some of which contain mucus.  Imaging studies reveal multiple mass lesions in the liver and lungs.  This patient's neoplasm most likely originated from which of the following locations?

Quizplus · Accepted Answer

This elderly patient with weight loss, anorexia, and iron deficiency anemia (IDA) likely has colon cancer, the third most common cancer among men (after prostate and lung). It is the most common gastrointestinal malignancy and one of the most common causes of IDA in the elderly. Right-sided colon cancers (eg, ascending colon) tend to grow as large, bulky masses that protrude into the colonic lumen due to the relatively large caliber of the ascending colon. They are more likely to bleed and therefore more likely to cause IDA. The bleeding is usually occult and detected by positive fecal occult blood testing. By contrast, left-sided tumors (eg, rectosigmoid colon) tend to be smaller. They often infiltrate the wall of the colon, encircling it and narrowing the lumen. Therefore, they are more likely to cause obstruction, and patients generally have altered bowel habits, abdominal distension, and nausea and vomiting (Choice E). Liver and lung are common sites of metastases. (Choice A) Malignant adrenal tumors are rare and typically present with symptoms of excessive hormone secretion (eg, Cushing syndrome). They would not cause IDA. (Choice C) Although this patient has lung lesions, most patients with lung cancer have referable symptoms at presentation (eg, cough, hemoptysis, dyspnea). Hepatic metastases can occur, but a colonic mass and IDA would be unusual. (Choice D) Prostate cancer typically develops at the gland periphery, so most patients do not have referable symptoms and urinary symptoms tend to occur late in the disease. Colonic metastases and IDA would be unusual. Educational objective: Colon adenocarcinoma is the most common gastrointestinal malignancy. Right-sided lesions are more likely to bleed and cause iron deficiency anemia; left-sided lesions tend to present with obstructing symptoms (eg, altered bowel habits, constipation, abdominal distension, nausea and vomiting). __________ References: Colorectal cancer statistics, 2014. (http://www.ncbi.nlm.nih.gov/pubmed/24639052) Tumor location is a prognostic factor in poorly differentiated adenocarcinoma, mucinous adenocarcinoma, and signet-ring cell carcinoma of the colon. (http://www.ncbi.nlm.nih.gov/pubmed/22052041)

A 65-Year-Old Man Is Found to Have Iron Deficiency Anemia