<unk>  (also<unk>  tumor or<unk>  tumor) is a slow-growing but often malignant type of neuroendocrine tumor, originating in the cells of the neuroendocrine system.<unk>  tumors are apudomas that arise from the enterochromaffin cells throughout the gut. They are most commonly found in the foregut (35.6% cases) with lungs, bronchus and trachea constituting 27.9% cases from where they rarely metastasized (except in case of pancreas). The next most common affected area is the small intestine especially the midgut (32.1% cases) with the highest proportion from the ileum at 14.9% of all cases. In cases of metastases it can lead to<unk> . This is due to the production of serotonin, which when released into the systemic circulation leads to symptoms of cutaneous flushing, diarrhea, bronchoconstriction and right-sided cardiac valve disease.<unk>  was first described by Siegfried Oberndorfer, a German pathologist in 1907. Endocrine related properties of<unk>  was described by Gosset and Masson in 1914.<unk>  tumor of the gastrointestinal tract may be classified based on the location into three subtypes (foregut, midgut, or hindgut).<unk>  tumor of the lung may be classified based on the histology into two subtypes (typical and atypical).<unk>  tumor of the ovary may be classified into four subtypes (insular, trabecular, strumal, and mucinous type). The pathophysiology of<unk>  tumor depends on the histological subtype. Genes involved in the pathogenesis of<unk>  tumor are β-catenin, NF1, and MEN1.<unk>  tumors originate from neuroendocrine cells. On microscopic histopathological analysis, gastrointestinal<unk>  is characterized by solid or small trabecular clusters of neuroendocrine cells with uniform nuclei and abundant granular or faintly staining (clear) cytoplasm. Common causes of<unk>  include genetic disorders (multiple endocrine neoplasia type 1 and neurofibromatosis type 1) and genetic mutations (gains involving chromosomes 5, 14, 17, and 19 and losses involving chromosomes 11 and 18).<unk>  must be differentiated from systemic mastocytosis, medullary thyroid carcinoma, irritable bowel<unk> , malignant neoplasms of the small intestine, benign cutaneous flushing, and recurrent idiopathic anaphylaxis. The incidence of<unk>  is estimated to be 2 cases per 100,000 individuals worldwide.<unk>  is a disease that tends to affect the elderly population. The median age at diagnosis is 60.9 years. Females are more commonly affected with<unk>  than males.<unk>  usually affects individuals of the Caucasian race. African American, Latin American, and Asian individuals are less likely to develop<unk> . Common risk factors in the development of<unk>  include age (50 years or older), gender (female), multiple endocrine neoplasia type 1, neurofibromatosis type 1, atrophic gastritis, pernicious anemia, and Zollinger-Ellison<unk> . There is insufficient evidence to recommend routine screening for<unk>  tumor. If left untreated, patients with<unk>  may progress to develop flushing, diarrhea, and<unk>  heart disease (valvular heart disease and cardiac dysrythmias). Common complications of<unk>  tumor include increased risk of falls and injury (from hypotension), bowel obstruction, gastrointestinal bleeding, right-sided heart failure, and fibrosis of the tricuspid valve and pulmonary valve, and rarely the mitral valve in cases with left sided involvement. Prognosis is generally good and the 5-year survival rate of patients with<unk>  is approximately 69.7%. According to The American Joint Committee on Cancer (AJCC), there are four stages of<unk>  based on the TNM staging sysytem. Symptoms of<unk>  tumor include flushing, diarrhea, wheezing, abdominal cramps, wheezing, and cough. Common physical examination findings of<unk>  include tachycardia, flushing, hypertension, hirsutism, pallor, cervical lymphadenopathy, wheezing, systolic or diastolic murmur, and lower limb edema. Laboratory findings consistent with the diagnosis of<unk>  include an elevated urinary 5-hydroxyindoleacetic acid (5-HIAA) and plasma levels of CgA levels. On ECG,<unk>  is characterized by high frequency of low-voltage qrs complexes. On chest x-ray, bronchial<unk>  tumor is characterized by the presence of round or oval opacities with sharp and notched margins, whereas thymic<unk>  tumor often demonstrates focal areas of necrosis or punctate calcifications. Chest CT scan may be helpful in the diagnosis of<unk>  tumor. On high-resolution CT scan of the chest, peripheral pulmonary<unk>  tumor is characterized by a solitary and round pulmonary nodule with a lobulated margin, whereas bronchial<unk>  tumor is characterized by a single well-defined, round or ovoid, hilar or perihilar mass with marked homogenous enhancement. On CT scan of the neck, thymic<unk>  tumor is characterized by a mass with heterogeneous attenuation. Abdominal MRI scan may be performed to detect metastases of<unk>  to liver and mesentery. There are no echocardiography findings associated with<unk> . Other imaging studies for<unk>  tumor include somatostatin scintigraphy with 111Indium-octreotide, bone scintigraphy with 99mTc-methylene diphosphonate (99mTcMDP), 123 I-metaiodobenzylguanidine (MIBG) scintigraphy, capsule endoscopy (CE), enteroscopy, and angiography. The predominant therapy for<unk>  is surgical resection. Supportive therapy for<unk>  includes somatostatin analogs, interferons, and radionuclides. Surgery is the mainstay of treatment for<unk>  tumor. The feasibility of surgery depends on the stage of<unk>  tumor at diagnosis. There is no established method for prevention of<unk> . There are no secondary preventive measures available for<unk> .
Carcinoid syndrome
Carcinomatosis
Hemochromatosis
Stress ulcer
Portal hypertension
Celiac disease
Cirrhosis
Alcoholic cardiomyopathy