Last reviewed and revised February 27, 2013
"You know, sometimes cancer isn't really cancer."
The first time I heard this, just a few years after I'd completed my medical training, I was shocked. But it's true. The line between cancer and benign isn't always black and white.
Myth: Cancer Is Cancer
Malignant (cancerous) cells have features that are generally unmistakable: They grow unchecked, have unusual shapes, have an abnormal number of nuclei (where the DNA is), and can spread to places they don't belong (metastasize).
Pathologists — specialists who examine cells under the microscope — train extensively to tell the difference between malignant and normal cells. But even experienced pathologists find it difficult to make a sure diagnosis of cancer.
Unless the pathology findings are clear-cut, a cancer diagnosis isn't always a simple yes or no. Non-cancerous cells can sometimes look like cancer cells. For example, a nearby infection may cause the cells in a lymph node to change in appearance. These "reactive" changes can be confused with changes suggestive of cancer.
The Pap test is a good example of how abnormal cells can blur the line between normal and cancerous. Cervical cells are collected during a pelvic exam and tested for human papilloma virus (HPV), an infection that may increase the risk of cervical cancer. A pathologist examins them under a microscope. There is widespread agreement that this test is worth having because it helps doctors diagnose cervical cancer and pre-cancerous changes while they are curable. Yet, the range of abnormal test results makes clear that the search for cancer is often full of uncertainty. Here are a few of the possible test results:
- Abnormal but of no definite importance – A Pap test report may read "ASC-US" which stands for "atypical squamous cells of undetermined significance." This result may occur after a vaginal infection or human papilloma virus infection (HPV). It usually requires only treatment of the infection (if one is present) and repeating the Pap test.
- Abnormal and potentially precancerous – A reading of "HSIL," which means high-grade squamous intraepithelial lesion, indicates that the cells are markedly different from normal cells and that there is a significant risk that they will progress to an invasive cancer. This finding usually leads doctors to recommend colposcopy (a more detailed examination of the cervix) or surgery to remove the abnormal tissue. Similarly, "ASC-H" (atypical squamous cells, high-grade), "AGC" (atypical glandular cells), and "high grade dysplasia" are findings of uncertain importance that may indicate a higher risk of cervical cancer.
- Cancer – Markedly abnormal cells collected during a Pap test may be malignant (cancerous), requiring colposcopy and surgery to remove the area of abnormal cells.
Women who follow the recommended schedule for Pap test are likely at some point to have one of the "pre-cancerous" abnormalities, even when no cancer is present. The uncertainty and occasional difference of agreement between pathologists who read Pap tests are a source of confusion, frustration, and, when a cancer is missed, tragedy.
When is cancer not really cancer? The clearest example is when a biopsy is reviewed and the original cancer diagnosis is "overturned." This is rare though.
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Other Cancer Myths and Misconceptions
Here are some other common misconceptions about cancer that I often hear from my patients:
- Cancer is one disease. When people talk about a cure for cancer, there's an implication that it's a single illness. In fact, we should think of cancer as many different diseases, with different causes, preventive measures and treatments. It's highly unlikely that a single treatment will cure all types of cancer. And certain cancers are already curable. Many types of skin cancers, for example, are curable just by removing them. Others types, such as cancer of the pancreas, are almost never cured.
- A biopsy can always diagnose cancer. Biopsy is almost always the best way to diagnose cancer, but it's not as perfect as you might think. If tissue is straddling the fine line between cancerous and non-cancerous, a biopsy may not be diagnostic. In the future, it's likely we'll have other ways to predict or diagnose cancer, such as the presence of proteins on the surface of cancer cells, genetic mutations and the appearance of tumors on certain imaging tests. None of these, however, are routinely better than a biopsy at the present time.
- Gather enough information and you'll get your answer. Doctors seem to have an endless number of blood tests and imaging tests (such as X-rays, MRIs, and CT scans) to evaluate a person with a suspicion of cancer. Unfortunately, extensive testing is generally no match for a biopsy. However, an imaging test like a CT scan, can help the doctor insert a biopsy instrument safely to take a tissue sample.
- A rising incidence of cancer is always a cause for concern. An increase in the number of new cancers could be due to better detection. And that's a good thing! For example, the incidence of breast cancer can change based on how conscientious women are about getting a mammogram every year. And a recent increase in melanoma, the deadliest form of skin cancer, is likely due to an increase in the number of skin biopsies rather than an increase in the disease itself. In other words, because of how we measure rates of cancer, an increase in the number of cancer diagnoses is not always due to more cancer.
- The prevalence of cancer is on the rise. It's true that more people currently have cancer now than in the past. But at least two of the reasons for this are positive developments: People are living longer (and advanced age is a risk factor for cancer) and people with cancer are living longer after diagnosis. Better cancer care — and better medical care in general — have contributed to the rising number of people living with cancer. Finally, there are more people on the earth today than ever before and that plays a role as well: More people means more people with cancer. However, the actual risk of cancer is falling.
- If you have cancer, it's always best to know. There may be a philosophical debate on this one, but I believe there are times when it's best not to know you have cancer. A good example is when a man has a slow-growing prostate cancer that poses no health threat. In fact, if a man lives long enough, there's a good chance he'll have prostate cancer but die of something else. Detection of these cancers only leads to unnecessary worry and, in some cases, treatments that have no real benefit but lots of side effects.
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The Bottom Line
Cancer is a source of great fear, confusion and misconception. While cancer is actually many different diseases, these two facts should provide some measure of reassurance:
- Modern medicine has achieved impressive advances in the fight against many types of cancer.
- There is much you can do to reduce your cancer risk.
Fortunately, this bit of good news is no myth.
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Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.