Endocrine System

Parathyroid Gland - Hyperplasia, Focal

Narrative

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.

Recommendations:

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

All Images

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.

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.

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.

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.

Authors and Reviewers

Authors

Robert R. Maronpot, DVM, MS, MPH, DACVP, DABT, FIATP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC

Georgette D. Hill, D.V.M., Ph.D.
Toxicologic Pathologist/Assistant Pathology Program Manager
Comparative Molecular Pathology Division
Integrated Laboratory Systems, Inc.
Research Triangle Park, NC

Reviewers

Thomas J. Rosol, DVM, PhD, DACVP
Professor of Veterinary Biosciences
Senior Advisor, Life Sciences, Technology Commercialization and Knowledge Transfer
The Ohio State University
Columbus, OH

Amy Brix, DVM, PhD, DACVP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC