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Colorectal cancer is the second leading cause of cancer death in U.S. men and women. It is the third most frequent cancer diagnosis. For the general population with average risk, guidelines recommend that screening tests, including the colonoscopy, start at 50 years old. During a colonoscopy, doctors examine the colon for the presence of polyps and other abnormalities and remove them. Several other screening tests exist, including CT colonography, blood tests, and stool DNA tests. The Yale Medicine Department of Pathology offers highly specialized expertise in this area. Most of the colorectal cancer cases are caught by screening colonoscopies, says Yale Medicine pathologist Joanna Gibson, MD, PhD.

What is the risk for colon cancer?

Most of the colorectal cancer cases are caught by screening colonoscopies, says Dr. Gibson. This is good news because early diagnosis offers the best odds of successful treatment. She adds: “Sometimes colon cancer is diagnosed because a person is complaining about a specific symptom, such as abdominal pain or anemia or feeling weak. Then they’ll have a colonoscopy to see what’s going on.” An increasing number of cases are being diagnosed in people under 50, Dr. Gibson says. “That group now accounts for between 20 to 25 percent of all cases,” she says.

How does a pathologist diagnose colon cancer?

The pathologist prepares a tissue sample for analysis, a complex endeavor that takes about a day. “The tissue samples have to be fixed – placed in a preservative – processed and put onto slides," Dr. Gibson says. "Then we go through various procedures where we add stains, which helps us to see what is actually in the tissue.”

The tissue is then examined under the microscope. “If I see abnormal growth, I classify it as benign (non-cancerous) or malignant (cancerous),” Dr. Gibson says. “Sometimes it can be difficult to make this distinction, in which case we may do additional studies of that tissue and we may also call the doctor who took the sample to discuss whether what he or she saw fits with the diagnosis."

Though pathologists don’t typically interact directly with patients, Dr. Gibson says she always keeps the person (and the colon-cleansing preparation she underwent before the colonoscopy) in the forefront of her mind.

“I'm always aware that this person went through an uncomfortable night to prepare for this procedure, and I don’t want to make them do it again,” she says. “So we do everything we can to make sure that we get the diagnosis right.”

How does a pathologist’s diagnosis inform colorectal cancer treatment?

A diagnosis of colon cancer isn’t just a “yes” or “no.” There are many different types, with a range of treatments for each. Common types of colon cancer include:

  • Adenocarcinoma
  • Lymphoma of the colon
  • Leiomyosarcoma
  • Neuroendocrine carcinoma

The difference between one tumor type and another is important, Dr. Gibson says. Some tumor types may have a spectrum of behavior that’s not always easy to predict.

For example, “sometimes certain low-grade malignant cells can behave in essentially a benign way. There may be a small nodule that is taken out and the patient never has any other recurrence. But some other varieties of that tumor type can spread to the liver or lymph nodes. We do a lot of studies on the tumor tissue sample to try and find features that we can measure in order to determine which patients need closer monitoring or to be treated more aggressively.”

What makes Yale Medicine’s approach to diagnosing colorectal cancer unique?

Yale Medicine’s pathologists are sub-specialists in their fields, bringing extensive expertise to their knowledge. “I did a fellowship in gastrointestinal pathology and the liver, and now my practice at Yale is focused on and limited to those areas,” Dr. Gibson says.

The pathologists at Yale Medicine are regularly asked to review diagnoses from community hospitals and other medical centers that don’t have sub-specialists on staff. “Most of the time they make the correct diagnosis,” Dr. Gibson says. “But occasionally, we review a case here and actually overturn the diagnosis or change the tumor type.”

Another Yale Medicine advantage, Dr. Gibson says, is that “we have a very open and collaborative culture here.” The department holds daily conferences where pathologists share their challenging cases to ensure that patients get the benefit of the expertise of many pathologists, not just one. Yale Medicine also has the technology to be able to offer molecular testing, which has become increasingly important in providing personalized cancer treatment.

“In addition to the numerous pathological tests we do, there may be several other molecular tests that we can report,” Dr. Gibson says. “These are different types of assays to look at the genes in the particular cancer a patient has, and that information is sometimes used to determine the type of medication a patient can get.”