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Parathyroid Gland - Hyperplasia, Focal

Image of hyperplasia, focal in the parathyroid gland from a male F344/N rat in a chronic study
Parathyroid Gland - Hyperplasia, Focal in a male F344/N rat from a chronic study. This low-magnification photomicrograph contains a focus of hyperplasia (arrow) with a growth pattern distinct from the adjacent parathyroid parenchyma.
Figure 1 of 4
Image of hyperplasia, focal in the parathyroid gland from a male F344/N rat in a chronic study
Parathyroid Gland - Hyperplasia, Focal in a male F344/N rat from a chronic study. Focal hyperplasia is characterized by cells with rounded nuclei and abundant hypertrophic cytoplasm but without compression of adjacent parathyroid parenchyma.
Figure 2 of 4
Image of hyperplasia, focal in the parathyroid gland from a male Wistar Han rat in a chronic study
Parathyroid Gland - Hyperplasia, Focal in a male Wistar Han rat from a chronic study. Two focal areas of hyperplasia with pale, enlarged cells (compared with surrounding parathyroid parenchyma) are present.
Figure 3 of 4
Image of hyperplasia, focal in the parathyroid gland from a male F344/N rat in a chronic study
Parathyroid Gland - Hyperplasia, Focal in a male F344/N rat from a chronic study. Two to three adjacent nests of hyperplastic foci are present; the pale staining of their hypertrophic cells makes them stand out from the normal parathyroid tissue.
Figure 4 of 4
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comment:

Parathyroid hyperplasia can be focal or diffuse and occurs in low incidence in rats and rarely in mice. Focal hyperplasia is a combination of hyperplasia and hypertrophy, with the hyperplastic foci standing out from the normal parathyroid parenchyma by virtue of structural alteration of the normal cords and/or differential tinctorial staining of the enlarged hypertrophic cells comprising the focal hyperplasia. There is negligible compression of surrounding parenchyma; in contrast, parathyroid adenomas cause compression of adjacent tissue and tend to be larger than hyperplasias. Severe focal hyperplasia can result in a grossly enlarged parathyroid. Focal parathyroid hyperplasia is potentially preneoplastic.

recommendation:

Focal parathyroid hyperplasia should be diagnosed and assigned a severity grade. If both parathyroids are involved, the diagnosis should be qualified as bilateral and the severity grade based on the more severely affect gland.

references:

Capen CC, DeLellis RA, Yarrington JT. 2002. Endocrine system. In: Handbook of Toxicologic Pathology, Vol 2 (Haschek WM, Rousseaux CG, Wallig MA, eds). Academic Press, New York, 681-783.
Abstract: http://www.sciencedirect.com/science/book/9780123302151

Rosol TJ, Capen CC. 1989. Tumors of the parathyroid gland and circulating parathyroid hormone-related protein associated with persistent hypercalcemia. Toxicol Pathol 17:346-356.
Full Text: http://tpx.sagepub.com/content/17/2/346.full.pdf

Seely JC, Hildebrandt PK.. 1990. Parathyroid gland. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, 537-543.
Abstract: http://www.ncbi.nlm.nih.gov/nlmcatalog/9002563

NTP is located at the National Institute of Environmental Health Sciences, part of the National Institutes of Health.