Neuroendocrine cells are present in various organs, and their function is to secrete hormones. Carcinoid tumors develop in these cells, resulting in increased production of the hormones. These tumors are slow-growing and do not cause symptoms in their early stages.
Carcinoid tumors originate from neuroendocrine cells and are slow-growing tumors. These tumors secrete a variety of hormones and chemical substances. These tumors occur in various organs in the body.
The most common site is the gastrointestinal tract, which constitutes about 60% of all carcinoids. The second most common site is the respiratory tract (tracheobronchial tree), which constitutes about 25% of primary carcinoid cancer cases. Other sites for the occurrence of these tumors include the ovaries and kidneys. The signs and symptoms are due to elevated levels of hormones in the blood.
There is an increasing trend in the development of neuroendocrine tumors. The incidence of neuroendocrine tumors is about 2 per 1,00,000 population and accounts for about 0.5% of all cancers. The incidence of gastrointestinal carcinoid cancer has increased by over ten times during the last 30 years. However, the trend of occurrence is decreasing for some types of carcinoid tumors, such as appendix carcinoid tumors.
Carcinoid tumors are malignant cells that secrete a significant amount of hormones and other substances into the blood. Carcinoid syndrome is characterized by the symptoms that are caused by elevated levels of those substances in the blood.
Almost 10% of people with carcinoid cancer experience carcinoid syndrome. The symptoms of carcinoid syndrome include head and neck flushing (resulting in the change of color from red to purple), excessive intestinal contraction (resulting in diarrhea and abdominal cramping), shortness of breath, wheezing (due to obstruction in the flow of air in the lungs), heart damage (that may cause edema of the legs and feet), low libido, and erectile dysfunction.
Some of the common locations where carcinoid cancers occur include:
The small intestine is the most common site for carcinoid tumor occurrence. Almost 40% of all GIT carcinoid cancers are found in the small intestine. A carcinoid tumor of the small bowel is usually diagnosed in patients aged between 60 and 70 years. The symptoms of small intestinal carcinoid tumors include diarrhea, abdominal pain, and small bowel obstruction. In advanced stages, this disease metastasizes to the liver and lymph nodes.
Most people with appendiceal carcinoid tumors are diagnosed between 40 and 50 years of age. In most cases, the diagnosis is made during the appendix surgery done for other diseases, such as appendicitis. The majority of the patients with this condition do not experience symptoms during the early stages, probably due to the location of these tumors in the distal appendix. At this location, there is a low obstruction risk.
Primary kidney carcinoid tumors are rare. Their clinical presentation, similar to the other renal tumors, makes their diagnosis challenging. These tumors have an uncertain pathology because neuroendocrine cells are absent in the pelvis, ureter, and renal parenchyma.
Carcinoid cancer in the lungs accounts for about 1-2% of all lung cancers. The carcinoids of the lung are divided into typical (low-grade) and atypical (high-grade) tumors. Although typical tumors frequently secrete growth hormones and corticotrophins, only less than 5% of the patients have carcinoid syndrome.
The carcinoid tumors of the ovaries are divided into stromal,
trabecular, mucinous, and insular. Of these, carcinoid syndrome occurs with the
insular type. A study has reported that most cases of carcinoid tumors of the
ovary occur in postmenopausal women.
They have the potential to metastasize and should be diagnosed and treated appropriately.
Pancreatic carcinoid tumors are neuroendocrine tumors that develop from the neuroendocrine cells of the pancreas. These tumors secrete different hormones, such as insulin, glucagon, gastrin, somatostatin, and serotonin. The symptoms of pancreatic carcinoid tumors depend upon the type and amount of hormones secreted by these tumors.
Rectal carcinoid tumors arise from the neuroendocrine cells present in the rectum. Not all rectal carcinoid tumors cause symptoms, and many of them are found incidentally. The symptoms present include abdominal pain, diarrhea, and flushing that are due to the secretion of serotonin by the tumor cells.
Stomach or gastric carcinoid tumors arise from the cells present in the stomach lining that are responsible for secreting hormones. The carcinoid tumor types of the stomach are Type 1, Type 2, and Type 3 tumors, of which Type 2 and Type 3 are aggressive and have the potential to metastasize.
Carcinoid tumors are cancerous and have the potential to metastasize to other organs. However, as compared to typical tumors, carcinoids are slow-growing, and most have a low potential to metastasize. Individuals with well-differentiated carcinoids have a relatively better prognosis, especially when the tumor is diagnosed at an early stage.
The stages of the carcinoid tumor of the stomach are:
At this stage, the tumor is confined to the lining of the internal tissues and has not spread to the deeper tissues.
At this stage of the carcinoid tumor, the malignant cells may invade the deeper tissues but are not spread outside the affected organ.
The tumor has invaded the nearby lymph nodes and tissues but has not spread to other organs.
The tumor, along with the lymph nodes and the nearby tissues, has also invaded the nearby organs.
Stage IV is the most advanced stage. At this stage, the tumor has spread to distant organs.
Carcinoid tumors are a subsection of neuroendocrine tumors. They occur in several organs, such as the pancreas, stomach, kidney, ovaries, rectum, lungs, and appendix. The stages of carcinoid tumors are from I to IV, with stage IV being the most advanced stage.