A carcinoid (also carcinoid tumor) is a slow-growing type of neuroendocrine tumor originating in the cells of the neuroendocrine system. In some cases, metastasis may occur. Carcinoid tumors of the midgut (jejunum, ileum, appendix, and cecum) are associated with carcinoid syndrome. Carcinoid tumors are the most common malignant tumor of the appendix, but they are most commonly associated with the small intestine, and they can also be found in the rectum and stomach. They are known to grow in the liver, but this finding is usually a manifestation of metastatic disease from a primary carcinoid occurring elsewhere in the body. They have a very slow growth rate compared to most malignant tumors. The median age at diagnosis for all patients with neuroendocrine tumors is 63 years. Signs and symptoms
While most carcinoids are asymptomatic through the natural life and are discovered only upon surgery for unrelated reasons (so-called coincidental carcinoids), all carcinoids are considered to have malignant potential. About 10% of carcinoids secrete excessive levels of a range of hormones, most notably serotonin (5-HT), causing:

Flushing (serotonin itself does not cause flushing). Potential causes of flushing in carcinoid syndrome include bradykinins, prostaglandins, tachykinins, substance P, and/or histamine, diarrhea, and heart problems. Because of serotonins growth-promoting effect on cardiac myocytes, a serotonin-secreting carcinoid tumour may cause a tricuspid valve disease syndrome, due to the proliferation of myocytes onto the valve. Diarrhea
Wheezing
Abdominal cramping
Peripheral edemaThe outflow of serotonin can cause a depletion of tryptophan leading to niacin deficiency.
The pharmaceutical company Bristol-Myers Squibb manufactures the drug under the trade name Zerit.It is also the first drug to be granted parallel track status in 1992, by the US Food and Drug Administration (FDA), which allowed for the agency to make Stavudine available to patients before being approved. Stavudine was submitted under the FDAs accelerated approval process. Through this process, Stavudines effectiveness was measured by its effect on the surrogate marker, CD4, instead of clinical endpoints. The FDA concluded that an increase in CD4 cell counts was an indicator of how effective the drug would be against AIDS and HIV infection. Stavudine was the fourth drug to be approved for the treatment of AIDS and HIV infection by the FDA on June 27, 1994. Even after approval, studies were continued to evaluate the clinical benefit of the drug. If there is no indication of clinical benefits, the accelerated approval may be withdrawn.In 2018, Mylan Pharmaceuticals discontinued manufacturing stavudine 20 mg, 30 mg, and 40 mg capsules. References
External links
"Stavudine". Drug Information Portal. U.S. National Library of Medicine.