Cancer of unknown primary origin overview
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Differentiating Cancer of Unknown Primary Origin from other Diseases |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: ; Roukoz A. Karam, M.D.[2]
Overview
Colorectal cancer is the third most commonly diagnosed cancer in the world, and accounts for 8% of all cancer-related deaths annually. There are both genetic and environmental factors that can increase the risk of colorectal carcinoma (CRC). The pathogenesis of colorectal carcinoma (CRC) involves the molecular pathways for both sporadic and colitis-associated CRC. There are both genetic and environmental causes of colorectal carcinoma (CRC). Colorectal cancer may be differentiated from other diseases that cause unexplained weight loss, unexplained loss of appetite, nausea, vomiting, diarrhea, anemia, jaundice, and fatigue, such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), hemorrhoids, anal fissures, and diverticular disease. Current guidelines recommend that colonoscopy is the optimal screening tool for colon cancer since it detects 98-99% of the cases. The progression from an edematous polyp to colorectal cancer may take 10-15 years. Colorectal cancer staging is an estimate of the amount of penetration of the cancer. Staging is based on the TNM classification system which depends on the extent of local invasion, the degree of lymph node involvement, and whether there is distant metastasis. The history of a patient with colorectal cancer may include a family history of polyps/colorectal cancer or a history of inflammatory bowel disease. Some symptoms that are associated with colorectal cancer are change in bowel habits, hematochezia, and rectal pain. Metastatic symptoms include dyspnea, abdominal pain, fractures, and confusion. Generally, the most common signs of colorectal cancer are emaciation, lethargy, and pallor Other signs include low-grade fever, discomfort on palpation, ascites, rectal bleeding, rectal mass, and jaundice. The laboratory findings associated with colorectal carcinoma are the following: Complete Blood Count (CBC), Fecal Occult Blood Tests (FOBT), serum CEA and CA 19-9 concentration, serum iron concentrations, serum vitamin B12 and folate concentrations, liver function tests, and pulmonary function tests. Chest radiography (CXR) is the initial imaging modality used in the detection of suspected pulmonary metastasis. CT scan is used to determine the extent of involvement on colon cancer, most commonly in the abdomen and lungs. Other imaging tests that can be used for colorectal cancer are MRI, ultrasound, endoscopy, PET scan, barium study, and angiography. A biopsy and genetic testing can be performed when a suspected lesion is found on colonoscopy. Chemotherapy is used to reduce the likelihood of metastasis developing, shrink tumor size, and slow tumor growth. Surgery remains the primary treatment while chemotherapy and/or radiotherapy may be recommended depending on the individual patient's staging and other medical factors. When colorectal cancer metastasizes, there will be a different approach than with a localized tumor. The most common site of metastasis is the liver, and the second most common is the lung.