An adenoma is a benign tumor of epithelial tissue with glandular origin, glandular characteristics, or both. Adenomas can grow from many glandular organs, including the adrenal glands, pituitary gland, thyroid, prostate, and others. Some adenomas grow from epithelial tissue in nonglandular areas but express glandular tissue structure (as can happen in familial polyposis coli). Although adenomas are benign, they should be treated as pre-cancerous. Over time adenomas may transform to become malignant, at which point they are called adenocarcinomas. Most adenomas do not transform. However, even though benign, they have the potential to cause serious health complications by compressing other structures (mass effect) and by producing large amounts of hormones in an unregulated, non-feedback-dependent manner (causing paraneoplastic syndromes). Some adenomas are too small to be seen macroscopically but can still cause clinical symptoms. Histopathology
Adenoma is a benign tumor of glandular tissue, such as the mucosa of stomach, small intestine, and colon, in which tumor cells form glands or gland like structures. In hollow organs (digestive tract), the adenoma grows into the lumen - adenomatous polyp or polypoid adenoma. Depending on the type of the insertion base, adenoma may be pedunculated (lobular head with a long slender stalk) or sessile (broad base). The adenomatous proliferation is characterized by different degrees of cell dysplasia (atypia or loss of normal differentiation of epithelium) irregular cells with hyperchromatic nuclei, stratified or pseudostratified nuclei, nucleolus, decreased mucosecretion, and mitosis. The architecture may be tubular, villous, or tubulo-villous. Basement membrane and muscularis mucosae are intact.
There are many types of benign salivary gland tumors, with names such as adenomas, oncocytomas, Warthin tumors, and benign mixed tumors (also known as pleomorphic adenomas). Benign tumors are almost always cured by surgery. Very rarely, they may become cancer if left untreated for a long time or if they are not completely removed and grow back. Its not clear exactly how benign tumors become cancers. There are many types of salivary gland cancers. Normal salivary glands are made up of several different types of cells, and tumors can start in any of these cell types. Salivary gland cancers are named according to which of these cell types they most look like when seen under a microscope. The main types of cancers are described below. Doctors usually give salivary cancers a grade (from 1 to 3, or from low to high), based on how abnormal the cancers look under a microscope. The grade gives a rough idea of how quickly it is likely to grow and spread. Grade 1 cancers (also called low grade or well differentiated) look very much like normal salivary gland cells. They tend to grow slowly and have a good outcome (prognosis). Grade 2 cancers (also called intermediate grade or moderately differentiated) have an appearance and outlook that is between grade 1 and grade 3 cancers. Grade 3 cancers (also called high grade or poorly differentiated) look very different from normal cells and often grow and/or spread quickly.