A carcinoid breast tumor is a slow-growing type of neuroendocrine tumor, which originates in the cells that function as part of the neuroendocrine system. Carcinoid tumors occuring as 'primary' breast lesions are extremely rare. Normally, a carcinoid breast tumor presenting in the breast will represent a metastasis from another area of the body. A carcinoid tumor is most likely to start in the 'hormone-producing' cells. That's why they are more likely to occur in the stomach, intestines, pancreas, and ovaries, rather than the breast. The exaxt cause of a carcinoid tumors, including carcinoid breast tumors, is unknown. In fact, carcinoid tumors, generally speaking, are far more common in men than in women. Histologically, carcinoid breast carcinoma can mimic the appearance of breast adenocarcinoma. Radiologically and clinically, carcinoid breast tumors can easily be mistaken for conventional breast cancers, even when the patient has a known history of a carcinoid tumor somewhere else in the body. So, probably the most important apsect of carcinoid breast tumor is to determine whether it is a primary or secondary tumor.
The endocrine system basically refers to the various cells in the body that produce hormones. Hormones, of course, are various chemical substances that are produced and enter the bloodstream and then exert a specific regulatory effect on the activity of other organs or cells. Because endocrine tumors arises from hormone-producing cells, the tumor itself can produce hormones and cause serious illness.
Carcinoid breast tumors usually develop from enterochromaffin cells. These are hormone-producing cells, and are most commonly found in the small intestine. They also occur in the appendix, rectum, colon, pancreas, ovaries, bile ducts, and liver, and there are a small amount of these cells in the breast. As a result, carcinoid tumors are most commonly found in the 'midgut' region, accounting for 75% to 87% of all cases of carcinoid cancers. The next most common locations for carcinoid carcinoma is in the repiratory tract, which accounts for about 28% of cases. A primary carcinoid breast tumor would be extremely rare. In fact, there is still a certain amount of professional dispute in terms of whether primary carcinoid breast cancer are frequent enough to justify a 'classification'. Those who argue against point to the fact that in most cases, a primary cancer site is eventually found somewhere else in the body. That other site may simply have missed detection at the time when the breast tumor was detected.
It is more likely that a carcinoid breast carcinoma would develop as a result of metastasis from another primary site, but even this is very rare. Overall, breast tumors which develop as a result from metastasis from other locations accounts for less than 2% of all breast tumors. Common cancers that have been know to metastasize to the breast include those from the prostate, lung,thyroid, kidney, the hematopoietic system, and malignant melanoma. If a woman has a clinically detectable breast mass, and a known history of carcinoid activity anywhere in the body, then suspsicion of metastasis rather than primary breast cancer should be high. It is very important to determine this, as there are serious ramifications regarding treatment.
A the present time, carcinoid tumors are considered to be distinctive from 'neuroendocrine breast tumors. Carcinoid tumors can really be thought of as one subset of neuroendocrine tumors, and they are far more likely to appear in the gastrointestinal tract (appendix, stomach, small intestine, colon, rectum) and in the lungs, rather than in the breast. Out of interest, there is an important distinction in terminology between neuroendocrine tumors and neuroendocrine cancers. A neuroendocrine breast tumor is one which looks benign but has the potential to spread to other parts of the body. A neuroendocrine cancer is an abnormal growth of altered neuroendocine cells, which may spread to other parts of the body.
Because carcinoid tumors develop from enterochromaffin cells, they often will retain the capability to produce the same hormones, and can still do so in large quantities. The hormones which are produced by carcinoid tumor cells can still criculate in the blood and cause quite a few adverse symptoms. This is termed 'carcinoid syndrome". Basically, it is a combination of symptoms, depending upon which kinds of hormones are released. Common hormones that are released by carcinoid tumors (including breast carcinoid tumors) are histamine, serotonin, bradykinin, and of course chromogranin A (which is a general marker for neuroendocrine tumors). Other symptoms that one might experience as the result of a carcinoid breast tumor would include diarrhea or skin flushing. One thing to remember though is that carcinoid tumors, including carcinoid breast tumors, would not likely produce any symptoms until late in the disease. Approximately 10% of patients with carcinoid breast tumors will experience the carcinoid syndrome.
Histologically, carcinoid breast carcinoma may mimic ductal adenocarcinoma of the breast. Carcinoid breast carcinoma cells will tend to have round to oval nuclei, with a fine, reticular chromatin pattern. Mitoses are generally rare, and necrosis is also quite often absent.
Treatment will depend on whether or not the carcinoid breast carcinoma is determined to be primary or secondary, and upon the 'stage' of tumor growth. If the breast carcinoid tumor is a result of metastasis, then lumpectomy alone should provide and effective treatment. Axillary dissection should be avoided, and mastectomy is also probably not necessary. It often requires a highly experienced cancer specialist to figure out the proper diagnosis, early in the proceedings. Typically either a lumpectomy or partial mastecomy is performed to remove the tumor. The patient will likely receive adjuvant radiation therapy, but chemical therapy has proven to have little benefit for carcinoid tumors and will not likely be used. Quite frequently, carcinoid breast tumors are treated with biological therapy (also sometimes called immunotherapy). Essentially, this means using the body's immune system to fight cancer. Immunotherapy has been shown to reduces the size of carcinoid tumors in as many as 17% of patients, and can also slow the growth of metastatic tumors. Some commonly used biological agents for treatment of carcinoid breast cancers include interferon and Sandostatin®. There are quite a few negative side-effects to biological treaments, however.
On the whole, the prognosis for carcinoid breast cancer is fairly positive. Most carcinoid breast tumors are quite slow-growing. The five year survival rate following the surgical removal of a carcinoid tumor which has not metastized can be as high as 90%. However, in about 45% of patients, metastasis is already present at the time of diagnosis, and in most cases a breast carcinoid tumor is in fact a metastasis from another site. Still, most women, even with a metastatic breast carcinoma will quite often live another 10 to 15 years. But if a carcinoid tumor has metastized to the liver, then the prognosis is poor.
Back to Types of Lesions list.