| Adenocarcinoma | |
|---|---|
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| Histopathology of typical features of adenocarcinoma onH&E stain, but in reality the visual features vary substantially, both by subtypes of adenocarcinoma as well as between individual cases. | |
| Specialty | Oncology,Pathology |
Adenocarcinoma[1] (/ˌædɪnoʊkɑːrsɪˈnoʊmə/; pluraladenocarcinomas oradenocarcinomata/ˌædɪnoʊkɑːrsɪˈnoʊmətə/;AC) (Greek ἀδήν (adḗn) "gland", Greek "karkínos", "cancer") is a type ofcanceroustumor that can occur in several parts of the body. It is defined asneoplasia ofepithelial tissue that hasglandular origin, glandular characteristics, or both. Adenocarcinomas are part of the larger grouping ofcarcinomas, but are also sometimes called by more precise terms omitting the word, where these exist. Thusinvasive ductal carcinoma, the most common form ofbreast cancer, is adenocarcinoma but does not use the term in its name—however, esophageal adenocarcinoma does to distinguish it from the other common type ofesophageal cancer, esophageal squamous cell carcinoma. Several of the most common forms of cancer are adenocarcinomas, and the various sorts of adenocarcinoma vary greatly in all their aspects, so that few useful generalizations can be made about them.
In the most specific usage, the glandular origin or traits areexocrine;endocrine gland tumors, such as aVIPoma, aninsulinoma, or apheochromocytoma, are typically not referred to as adenocarcinomas but rather are often calledneuroendocrine tumors. Epithelial tissue sometimes includes, but is not limited to, the surface layer of skin, glands, and a variety of other tissue that lines the cavities and organs of the body. Epithelial tissue can be derived embryologically from any of thegerm layers (ectoderm,endoderm, ormesoderm). To be classified as adenocarcinoma, the cells do not necessarily need to be part of agland, as long as they have secretory properties. Adenocarcinoma is themalignant counterpart toadenoma, which is thebenign form of suchtumors. Sometimes adenomastransform into adenocarcinomas, but most do not.
Well-differentiated adenocarcinomas tend to resemble the glandular tissue that they are derived from, while poorly differentiated adenocarcinomas may not. Bystaining the cells from abiopsy, apathologist can determine whether the tumor is an adenocarcinoma or some other type of cancer. Adenocarcinomas can arise in many tissues of the body owing to the ubiquitous occurrence of glands within the body, and, more fundamentally, to thepotency of epithelial cells. While each gland may not be secreting the same substance, as long as there is an exocrine function to the cell, it is considered glandular and its malignant form is therefore named adenocarcinoma.
Examples of cancers where adenocarcinomas are a common form:
Mostbreast cancers start in the ducts orlobules, and are adenocarcinomas. The three most common histopathological types collectively represent approximately three-quarters of breast cancers:
The vast majority ofcolorectal cancers are adenocarcinomas. This is because thecolon has numerous glands. Normal colonic glands tend to be simple and tubular in appearance with a mixture ofmucus-secretinggoblet cells and water-absorbing cells. These glands secrete mucus into thelumen of the colon to lubricate the feces as they pass towards the rectum.[7]
When these glands undergo a number of changes at the genetic level, they proceed in a predictable manner as they move from benign to an invasive, malignant colon cancer. In their research paper "Lessons from Hereditary Colorectal Cancer", Vogelstein, et al., suggested that colon cells lose theAPC tumor suppressor gene and become a small polyp. Next, they suggested thatk-Ras becomes activated and the polyp becomes a small, benign adenoma. The adenoma, lacking the "carcinoma" attached to the end of it, suggests that it is a benign version of the malignant adenocarcinoma. The gastroenterologist uses a colonoscopy to find and remove these adenomas and polyps to prevent them from continuing to acquire genetic changes that will lead to an invasive adenocarcinoma. Vogelstein et al. went on to suggest that loss of theDCC gene and ofp53 result in a malignant adenocarcinoma.[8]
Nearly 40% of lung cancers are adenocarcinomas, which usually originate in peripheral lung tissue.[10] Most cases of adenocarcinoma are associated with smoking; however, among people who have smoked fewer than 100 cigarettes in their lifetimes ("never-smokers"),[11] adenocarcinoma is the most common form of lung cancer.[12] A subtype of adenocarcinoma, thebronchioloalveolar carcinoma, is more common in female never-smokers, and may have a better long-term survival.[13]
This cancer usually is seen peripherally in the lungs, as opposed tosmall cell lung cancer andsquamous cell lung cancer, which both tend to be more centrally located.[14][15]
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