William of Ockham, a 14th-century Franciscan friar, is widely credited as the originator of Occam's Razor (also "Ockham's"), a principle that states, in the barest of terms, that "the simplest explanation tends to be the right one." In the practice of medicine, this principle is often simplified even further, to the famous (or infamous) "When you hear hoofbeats, think horses, not zebras".

This principle is so commonly accepted in modern medical practice that it is often used as the rationale for medical decision-making. The Journal of the American Board of American Practice refers to it as "an evidence-based model of accountability", explaining the initial diagnosis-making protocol as follows:

"When a patient comes to the clinic with a new complaint, the often wide array of possible causes creates uncertainty about the optimal evaluation and treatment. Selecting an approach to evaluation involves values that range from ruling out all disease processes (all zebras) regardless of cost to limiting cost by looking only for those that are likely (assuming all hoof beats are caused by horses)." ( of the American Board of Family Practice, Vol. 13, Issue 6 424-429 c2000)

Such an explanation sounds rational and reasonable, especially when one considers the high cost of medical testing, the invasive nature of many high-level tests, and the limitless number of possible causes for any physical ailment. After all, sometimes a stomachache is just a stomachache, the hoofbeats are being caused by horses, and all one needs is a bicarbonate of soda. But what if your stomachache is not just a stomachache? What if the hoofbeats are being caused by zebras and not horses? What if the cause of your complaint is something serious, complex, little-known by the medical community and the public at large? What if the cause of your complaint is something that can masquerade as a dozen other conditions? What if you are facing carcinoid cancer?

If you have never heard of carcinoid cancer, you are not alone. It is just one of a group of rare cancers sometimes referred to as "zebra cancers". Carcinoid simply does not fit into the "evidence-based model of accountability" that so many medical practitioners utilize today. Although the occurrence of carcinoid tumors is considered to be on the rise, it is still a fairly rare cancer. While the American Cancer Society estimates that in 2007, there will be 178, 480 diagnoses of breast cancer and 234, 460 diagnoses of prostate cancer in the U.S., The Carcinoid Cancer Foundation estimates approximately just eleven thousand new diagnoses of carcinoid each year.

Complicating matters even further for carcinoid patients and the medical practitioners trying to find a cause for their ailments is the fact that many carcinoid patients remain asymptomatic for years, only discovering the existence of a tumor through secondary causes such as a bowel obstruction or an appendectomy. So how is one to seek care for such a condition, if even many doctors are unaware of it? The key is to be aware yourself of the symptoms, and to make sure that this information is disseminated to medical professionals and to the general public at large.

What is carcinoid cancer? Carcinoid is usually a very slow-growing cancer which often originates in the hormone-producing cells that line the small intestine or in other cells of the digestive tract. Carcinoid tumors are found mostly in the gastrointestinal system, but also occur, though more rarely, in other organs as well, such as the pancreas and the lungs. Because carcinoid tumors originate in hormone-producing cells, they often produce large quantities of various types of hormones (which type of hormone may depend upon the specific site of origin of the tumor). These elevated hormone levels are what ultimately cause a group of symptoms known collectively as carcinoid syndrome.

What are the symptoms of carcinoid syndrome?

• Intermittent or consistent abdominal pain, usually above the waist; sometimes the pain may be very severe and may last for days
• Chronic diarrhea
• Shortness of breath or wheezing
• Facial or body "flushing"-turning red or red with blotches. This may be dry or moist flushing.
• Erratic blood pressure readings, varying from very high to very low
• A bluish tint to the skin (cyanosis)
• Swelling of certain body parts (face, hands, feet)
• Fever
• Heart damage
• Malnutrition (caused by malabsorption of foods)
• Reduced libido
• Skin lesions

Because carcinoid syndrome may mimic symptoms for some other common ailments, diagnoses of the following conditions may, in reality, be misdiagnoses of carcinoid:
• Irritable Bowel Syndrome
• Crohn's Disease
• Asthma
• Rosacea

It should be noted that these symptoms only serve as possible clues to the presence of carcinoid tumors; they are not to be considered a reliable diagnostic tool, since as many as twenty to thirty percent of carcinoid patients are completely asymptomatic.

The fact that carcinoid syndrome mimics symptoms for so many other common ailments really highlights the need for a "zebras vs. horses" approach by medical practitioners in these cases. A physician who is unfamiliar with the symptoms of carcinoid syndrome may supply a patient with a diagnosis of asthma and leave it at that, never looking into the larger group of symptoms as a whole, and thus never examining the possibility of a more serious cause behind the patient's suffering. Further complicating the matter of diagnosing carcinoid is the fact that, due to the often slow growth of carcinoid tumors, some patients may go for years exhibiting few, mild, or rarely, no symptoms at all, which can make early diagnosis difficult. According to, " Most early-stage carcinoids are discovered incidentally during colonoscopies, regular physical exams, appendectomies, or other surgeries." With such formidable obstacles to obtaining a correct diagnosis, how should patients and their medical practitioners proceed?

If a tumor is "accidentally" discovered, through surgery, a bowel obstruction, or other incident, that is actually the easy path to a diagnosis. Medical practitioners would proceed to a biopsy of the mass and thus discover the presence of carcinoid. But if a patient is suffering from carcinoid syndrome, without the presence of a tumor to alert the physician to the cancer, distinguishing "the horses" from "the zebras" would then involve a few simple tests:

Tests for Carcinoid: Most carcinoid syndrome cases exhibit an increase in at least one of the many endocrine chemical products, so the first tests that should be done are a check of a patient's levels of blood serum serotonin (a neurotransmitter which can be produced by some carcinoids in various amounts); tryptophan (an amino acid) and Chromogranin A (considered the gold standard of diagnoses for carcinoid) in a patient's blood and/or urine (done with a 24-hour Urine 5HIAA test). These tests are an excellent starting point to obtaining a correct diagnosis, but patients should know that even these tests may fail to find carcinoid when it is present. Approximately fifteen percent of carcinoid patients may have all blood markers and 5HIAA urine tests in normal range. According to, "Urine 5HIAA will correctly diagnose all midgut (the middle part of the alimentary canal from the stomach or entrance from the bile duct to, or including, the large intestine) carcinoid tumors causing carcinoid syndrome, but only half of foregut (the anterior part of the alimentary canal from the mouth to the duodenum at the entrance of the bile duct) carcinoids causing syndrome, and almost none of hindgut (the posterior part of the alimentary canal, including the rectum and sometimes the large intestine) carcinoid tumors.

An additional test, an Octreoscan, may be performed as well to confirm or rule out an initial diagnosis through the blood and urine tests. The patient in this test is injected with a nuclear tag (Indium111), then scanned at twenty-four, forty-eight, and possibly seventy-two hours after the injection. Carcinoid cancers, lymphomas, even some breast cancers, contain receptors that, with the injection of this nuclear tag, will light up on a scan film. While the Octreoscan is a very good test, it is still not perfect, as roughly two percent of carcinoid tumors do not have the necessary receptors and thus do not show up on an Octreoscan. A CT scan can also detect tumors, but it is not considered by experts to be the most effective screening tool for carcinoid.

If a mass is found during any of these scans, a tissue biopsy must then be performed. Biopsy is the critical step in diagnosing carcinoid. In fact, according to Dr. Eugene A. Woltering of Louisiana State Medical Center, who is considered to be a leading expert in this field, "Fifty percent of tumors never show up on any scan. Biopsy is the only way to tell what a mass is for sure." In those cases where a tumor fails to be detected by a scan, patients may then need to undergo exploratory surgery. This can turn up tumors that the scans have missed, allowing for subsequent tissue biopsies to be examined and a correct diagnosis to be made. Upon biopsy, many carcinoid experts also order a specific proliferation test called a Ki-67 to determine if the cells are typical (slow-growing) or atypical (fast-growing). Only if the cells are atypical will the tumors respond to chemotherapy.

What is the treatment once carcinoid is diagnosed? Many carcinoid experts do not believe there is a cure for carcinoid, but do believe that it can be controlled. The most effective treatment for carcinoid is the complete, surgical removal of the tumor(s). If any microscopic cells remain, they could " show up after a number of years, requiring treatment, or death could ensue." ( Chemotherapy is only effective in one-third of all midgut carcinoids and a slightly larger percentage of foregut carcinoids (if they are fast-growing). Embolization treatment of the tumor is another possibility. This is a non-surgical, minimally invasive procedure, performed by interventional radiologists and neuroradiologists, which involves selective blocking of the blood vessels supplying the tumor. The idea is to cut off the blood supply to the tumor, thereby slowing its growth.

Many carcinoid patients opt to take the drug Sandostatin (Octreotide). This drug is similar in composition to somatostatin, a substance which occurs naturally in the body and functions to prevent the release of hormones in the body. As the increased release of hormones by the carcinoid tumor is what causes the symptoms of carcinoid syndrome in the first place, it is thought that taking Sandostatin can reduce the severity of the symptoms and may impede the progression of the disease, though its effect from patient to patient can vary widely.

What is the prognosis for patients with carcinoid cancer? As with any type of cancer, early detection is critical. If one is asymptomatic, there isn't any reason to specifically run out and have a battery of tests done. However, the fact that carcinoid can grow undetected for years without causing symptoms makes having regular physical exams, including colonoscopies, blood pressure tests, and blood and urine tests, a critical part of protecting yourself against this type of cancer. If a tumor has not spread, which is generally the case with asymptomatic carcinoid discovered through other medical procedures, the five-year survival rate is eighty-one percent (compare that to prostate cancer, which is eighty-two percent). If the tumor has spread to adjacent organs, the five-year survival rate drops dramatically to forty-seven percent; untreated carcinoid that has metastasized (spread to a wider region in the body) has a five-year survival rate of just eighteen percent. Just because carcinoid usually grows slowly does not make it any less lethal; what it does mean is that the window of opportunity in which carcinoid can be highly treatable is much larger than for other more rapidly-growing cancers. Again, early detection is key.

Because this diagnosis can be so elusive, and because so many medical practitioners (even many oncologists) remain unaware of the implications of the group of symptoms that make up carcinoid syndrome, it is critical for patients to educate themselves, to be their own advocates, and to make sure that their doctors do not dismiss their concerns out of hand. If you are experiencing, any of the symptoms listed earlier in this article, address your concerns with your doctor. Do not allow your concerns to be attributed to stress or anxiety. If you find that your doctor is unwilling to investigate further, find another doctor. Dr. Woltering illustrates this critical piece of advice with his "Yellow Corvette" parable, which is paraphrased here:

A man with sixty thousand dollars (cash) in his pocket walks onto a dealer's lot and tells the dealer that he's wanted to buy a yellow Corvette his entire life and that he is ready to buy one today. The dealer tells him he has red, blue, silver, black, and gold Corvettes in stock on the lot, but has no yellow ones and will not order any yellow ones. What should the customer do? Obviously, he should go to another dealer. "If you are being treated by a doctor who is not knowledgeable about this disease (and doesn't want to get educated on this disease) or will not work with you and a carcinoid expert to get you the best care available-you need a new doctor." ( In other words, don't settle for what's "on the lot".

The incidence of carcinoid cancer is thought to be on the rise, thus, the amount of available information about carcinoid is also increasing. Take advantage of this fact and do your research, become knowledgeable, and educate those around you-because sometimes, those hoofbeats are just horses. But maybe, just maybe, the sound you're hearing is a stampede of zebras, and it is not your doctor who will be the one caught under their hooves. It is you.

Sources: The Carcinoid Cancer Foundation; in addition, Dr. Eugene Woltering, M.D., FACS, Louisiana State Medical Center; and Karen Sharff Nelson, patient and advocate.

Disclaimer: This Buzzle article is for informative purposes only, and should not be used as a replacement for expert medical advice.