Bowel Cancer Types, Detection, Diagnosis

A physician may decide to initiate exploratory tests either because the patient is showing one or more of the symptoms associated with CRC or routine screening has detected the presence of pre-cancerous, benign tumors in the colon, before the patient is experiencing any symptoms.

Digital rectal exam (DRE): This straightforward procedure involves the physician inserting a lubricated, gloved finger into the rectum to feel for the presence of abnormalities.

Fecal occult blood test (FOBT): This simple and inexpensive test to establish the presence of blood in the stool is recommended for all people fifty years and over who are considered to be at average risk. The test should be performed on an annual basis. The patient is simply required to submit a stool sample. Your physician can provide instructions.

Double contrast barium enema (DCBE): By using contrast media and x-rays, the physician is able to locate any blockages or abnormalities in the lining of the lower bowel.

Sigmoidoscopy: This requires no anesthesia and involves the examination of the rectum and lower colon using a lighted instrument called a sigmoidoscope.

Colonoscopy: This procedure involves an examination of the rectum and the entire colon using a viewing instrument called a colonoscope.

Often, during sigmoidoscopy or colonoscopy, the physician also performs a routine polypectomy (the removal of polyps).

If the tests reveal any suspect tissue or the presence of polyps, the tissue removed during a biopsy or polypectomy will be examined. A pathologist studies the biopsied tissue under a microscope to establish whether the tissue is malignant or benign.

If the pathologist or radiologist diagnoses cancer, the malignant tissue is then "staged" based on the appearance of the sample and by performing further tests involving x-rays to assess the spread of the disease.

Adenocarcinoma is by far the most common type. A malignant tumor of the lining of the large intestine is generally referred to as a "carcinoma" (not to be confused with another condition called carcinoid tumor).

Carcinoid tumor is a distinct type of tumor that secretes serotonin and may cause facial flushing.

Lymphoma and sarcoma are also malignancies that may affect the colon. Lymphoma of the colon generally has a more favorable prognosis than adenocarcinoma. Lymphomas and sarcomas represent a minority of CRC cases.

Gastrointestinal stromal tumor (GIST) are relatively common, however the majority of gastrointestinal stromal tumors occur in the stomach, with only about five percent occurring in the colon and rectum.