: A condition in which there is an increase in the number of normal cells in a tissue or organ.
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An increase in number of normal cells in a tissue or organ, excluding tumor formation, whereby the bulk of the part or organ may be increased. SEE ALSO: hypertrophy. SYN: numerical hypertrophy, quantitative hypertrophy. [hyper- + G. plasis, a molding]
- angiofollicular mediastinal lymph node h. SYN: benign giant lymph node h..
- angiolymphoid h. with eosinophilia solitary or multiple small benign cutaneous erythematous nodules, occurring mainly on the head and neck in young adults, characterized by dermal proliferation of blood vessel s with vacuolated histiocytoid endothelial cells and with a varied infiltrate of eosinophils, lymphocytes which may form follicles, and histiocytes. SYN: Kimura disease.
- atypical endometrial h. increase in the number of glands, which have little, if any, stroma separating them but retain an orderly architecture distinguishing them from adenocarcinoma.
- atypical melanocytic h. proliferation of melanocytes showing nuclear atypicality, especially as scattered single cells high in the epidermis; interpreted by some pathologists as malignant melanoma in situ.
- basal cell h. increase in the number of cells in an epithelium resembling the basal cells.
- benign giant lymph node h. solitary masses of lymphoid tissue containing concentric perivascular aggregates of lymphocytes, occurring usually in the mediastinum or hilar region of young adults; similar changes have been reported outside the mediastinum and, if associated with interfollicular sheets of plasma cells, may progress to lymphoma or plasmacytoma. SYN: angiofollicular mediastinal lymph node h., Castleman disease.
- benign prostatic h. progressive enlargement of the prostate due to h. of both glandular and stromal components, typically beginning in the fifth decade and sometimes causing obstructive or irritative symptoms, or both; does not evolve into cancer.
- complex endometrial h. closely packed endometrial glands, with a single layer of cells with slightly enlarged nuclei that are generally basally located. SYN: adenomatous h..
- congenital adrenal h. a group of autosomal recessively inherited disorders associated with a deficiency of one of the enzymes involved in cortisol biosynthesis, resulting in elevation of ACTH levels and overproduction and accumulation of cortisol precursors proximal to the block; androgens are produced in excess, causing virilization. The most common disorder is the 21-hydroxylase deficiency, caused by mutation in the cytochrome P450 21-hydroxylase gene (CYP21) on chromosome 6p. There are four major types with some clinical similarities but distinctive genetic and biochemical differences: 1) the salt-losing form [MIM*201710, MIM*201810, and MIM*201910], 2) the hypertensive form [MIM*202010 and MIM*202110], 3) the simple virilizing form [MIM*201910], and 4) the pseudohermaphrodite form [MIM*201810 and MIM*202110].
- congenital virilizing adrenal h. a series of inherited inborn errors of metabolism with h. of the adrenal cortex and overproduction of virilizing hormones. Most common forms are due to partial or complete 21-hydroxylase deficiency, leading to increased ACTH production by the pituitary, stimulating adrenal growth and function. Severe form is characterized by salt-losing state.
- cystic h. formation of multiple retention cysts from obstruction of ducts or glands by h. of the lining epithelium, as in fibrocystic disease of the breast and metropathia hemorrhagica.
- cystic h. of the breast SYN: fibrocystic condition of the breast.
- ductal h. h. characterized by intraductal proliferation of epithelial cells, e.g., in the breast.
- endometrial h. increase in the number of endometrial glands, usually secondary to hyperestrinism; classified as simple h., complex h., or complex h. with atypia; the latter may progress to adenocarcinoma.
- fibromuscular h. thickening of arterial media by fibrosis and muscular h., usually involving the renal arteries and causing multifocal stenosis and hypertension; a variety of fibromuscular dysplasia.
- focal epithelial h. multiple soft nodular lesions of the lips, buccal mucosa, tongue, and other oral sites in children and adolescents; lesions spontaneously regress after a period of several months, and have been attributed to papovaviruses. SYN: Heck disease.
- gingival h. gingival enlargement due to proliferation of fibrous connective tissue. SYN: gingival proliferation.
- inflammatory fibrous h. overgrowth of tissue in the mucobuccal or labial fold, induced by chronic trauma from ill-fitting dentures. SYN: denture h., epulis fissuratum.
- inflammatory papillary h. closely arranged papules of the palatal mucosa underlying an ill-fitting denture. SYN: palatal papillomatosis.
- intravascular papillary endothelial h. a benign florid papillary endothelial proliferation within the veins of the skin or subcutis, less often in visceral blood vessel s.
- neuronal h. increased numbers of ganglion cells with myenteric plexus h. and increased acetylcholinesterase activity in nerves of the mucosa and submucosa. Clinically, neuronal h. mimics Hirschsprung disease. Similar findings are seen in patients with multiple endocrine neoplasia syndrome, type IIB, and in neurofibromatosis. SYN: hyperganglionosis, neuronal intestinal dysplasia.
- nodular h. of prostate glandular and stromal h. occurring very commonly in the transition zone and anterior fibromuscular stroma of older men, forming nodules that may increasingly obstruct the urethra.
- nodular regenerative h. SYN: nodular transformation of the liver.
- pseudoepitheliomatous h., pseudocarcinomatous h. a benign marked increase and downgrowth of epidermal cells, observed in chronic inflammatory dermatoses and over some dermal neoplasms and nevi; microscopically, it resembles well-differentiated squamous cell carcinoma.
- senile sebaceous h. h. of mature sebaceous glands, forming a nodule on the skin of the face or forehead in elderly persons.
- simple endometrial h. increase in the amount of endometrial tissue, with glands separated by abundant stroma. SYN: Swiss cheese endometrium.
- squamous cell h. increase in the number of cells in a squamous epithelium. SYN: hypertrophic dystrophy.
- verrucous h. h. of the oral mucosa, occurring in the elderly, characterized by sharp or blunt upward papillary projections of squamous epithelium.

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hy·per·pla·sia .hī-pər-'plā-zh(ē-)ə n an abnormal or unusual increase in the elements composing a part (as cells composing a tissue) see benign prostatic hyperplasia
hy·per·plas·tic -'plas-tik adj
hy·per·plas·ti·cal·ly -ti-k(ə-)lē adv

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the increased production and growth of normal cells in a tissue or organ. The affected part becomes larger but retains its normal form, as in benign prostatic hyperplasia (see prostate gland). During pregnancy the breasts grow in this manner. See also endometrial hyperplasia. Compare hypertrophy, neoplasia.

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hy·per·pla·sia (hi″pər-plaґzhə) [hyper- + -plasia] abnormal multiplication or increase in the number of normal cells in normal arrangement in a tissue. See also hypertrophy and proliferation. hyperplastic adj

Medical dictionary. 2011.

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