Endocrine System

Pituitary Gland - Cyst

Narrative

Comment:

Pituitary cysts in the pars distalis are frequent incidental findings in rats more than a year old and in mice. Most are remnants of the craniopharyngeal (Rathke's) pouch and are distinct from Rathke's cleft dilation that is localized between the pars distalis and pars intermedia. Pituitary cysts may be single or multiple, may contain eosinophilic proteinaceous or mucoproteinaceous fluid, are often lined by ciliated cuboidal to columnar cells, and typically do not compress surrounding parenchyma. The ciliated epithelial lining may be incomplete. The epithelial lining distinguishes them from angiectasis and/or enlarged vascular sinuses and from cystic degeneration, where irregular edges are lined by degenerating secretory cells. Occasionally, the adenohypophysis contains small follicle-like structures that are incidental and should not be diagnosed as cysts. The presence of multiple epithelium-lined cysts in the pars nervosa (arrows, Figure 4 and Figure 5) suggests an origin from the infundibular lumen. A dilated Rathke’s cleft (asterisks, Figure 4 and Figure 5) may also be present.

The majority of the literature dealing with pituitary cysts makes reference to a craniopharyngeal origin and further indicates that Rathke's pouch is part of the craniopharyngeal structure. Consequently, cysts of Rathke's pouch and craniopharyngeal cysts are synonymous. Determination of the origin of specific cysts may be difficult.

Recommendations:

While attempting to distinguish the origin of pituitary cysts is not critical, these cysts should be diagnosed whenever present, and the part of the pituitary in which the cysts occur should be indicated in the diagnosis (e.g., Pituitary Gland, Pars nervosa - Cyst). If there are multiple cysts, the modifier "multiple" should be included in the diagnosis. Since chronic studies may incorporate in utero exposure, developmental alterations potentially related to treatment could influence the ultimate presence and appearance of pituitary cysts. A severity grade would be appropriate if there is a potential treatment-related effect on the occurrence or severity of this change.

References:

Capen CC. 1983. Functional and pathologic interrelationships of the pituitary gland and hypothalamus. In: Endocrine System (Jones TC, Mohr U, Hunt RD, eds). Springer, New York, 103-120.

Abstract: http://www.springer.com/medicine/pathology/book/978-3-642-96722-1

Capen CC, DeLellis RA, Yarrington JT. 1991. Endocrine system. In: Handbook of Toxicologic Pathology (Haschek WM, Rousseaux CG, eds). Academic Press, New York, 697-705.

Abstract: http://www.sciencedirect.com/science/book/9780123302151

Carlton WW, Gries CL. 1983. Cysts, pituitary; rat, mouse, and hamster. In: Endocrine System (Jones TC, Mohr U, Hunt RD, eds). Springer, New York, 161-163.

Abstract: http://www.springer.com/medicine/pathology/book/978-3-642-96722-1

Gon G, Nakamura F, Ishikawa H. 1987. Cystlike structures derived from the marginal cells of Rathke's cleft in rat pituitary grafts. Cell Tissue Res 250:29-33.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/3652164

Herrick E, McCormack S. 1952. The occurrence and nature of cysts in the pituitary of fowls and rats. Trans Kans Acad Sci 55:178-183.

Abstract: http://www.jstor.org/stable/3625875

Iwata H, Hosoi M, Miyajima R, Yamamoto S, Mikami S, Yamakawa S, Enomoto M, Imazawa T, Mitsumori K. 2000. Morphogenesis of craniopharyngeal derivatives in the neurohypophysis of Fisher 344 rats: Abnormally developed epithelial tissues including parotid glands derived from the stomatodeum. Toxicol Pathol 28:568-574.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/10930044

Kouki T, Imai H, Aoto K, Eto K, Shioda S, Kawamura K, Kikuyama S. 2001. Developmental origin of the rat adenohypophysis prior to the formation of Rathke's pouch. Development 128:959-963.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/11222149

Lansdown AB, Grasso P 1971. Histological observations on a Rathke's cleft abnormality in a laboratory rat. J Comp Pathol 81:141-144.

Abstract: http://www.sciencedirect.com/science/article/pii/0021997571900661

MacKenzie WF, Boorman GA. 1991. Pituitary gland. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman G, Eustis S, Elwell M, Montgomery CA, MacKenzie W, eds). Academic Press, San Diego, 485-500.

Abstract: http://www.ncbi.nlm.nih.gov/nlmcatalog/9002563

Mahler J, Elwell M. 1999. The pituitary gland. In: Pathology of the Mouse: Reference and Atlas (Maronpot RR, Boorman GA, Gaul BW, eds). Cache River Press, Vienna, IL, 491-508.

Abstract: http://www.cacheriverpress.com/books/pathmouse.htm

Morton D, Tekeli S. 1997. "Have you seen this?" Pituitary cysts in a mouse. Toxicol Pathol 25:333.

Full Text: http://tpx.sagepub.com/content/25/3/333.long

Quintanar-Stephano A, Munoz Fernandez L, Quintanar JL, Kovacs K. 2001. Cysts in the rat adenohypophysis: Incidence and histology. Endocr Pathol 12:63-71.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/11478270

Watanabe YG. 1991 The occurrence and developmental origin of epithelial cysts in the rat and mouse adenohypophysis. Arch Histol Cytol 54:511-518.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/1665339

All Images

Pituitary Gland - Cyst in a female Harlan Sprague-Dawley rat from a chronic study. A cyst filled with pale eosinophilic proteinaceous fluid is present in the pars distalis.

Pituitary Gland - Cyst in a female Harlan Sprague-Dawley rat from a chronic study. Higher magnification of Figure 1 shows that the cyst is partially lined by tall cuboidal ciliated epithelium.

Pituitary Gland - Cyst in a male F344/n rat from a chronic study. The cysts in the pars distalis are lined by ciliated cuboidal cells and contain flocculant eosinophilic proteinaceous material.

Pituitary Gland - Cyst, multiple in a female F344/N rat from a chronic study. Multiple cysts are present in the pars nervosa (arrows), as well as a dilated persistent Rathke's cleft (asterisks), are filled with eosinophilic proteinaceous material., basic_html

Pituitary Gland - Cyst, multiple in a female F344/N rat from a chronic study. Higher magnification of Figure 4 shows the cysts in the pars nervosa (arrows) and the dilated persistent Rathke's cleft (asterisks) in greater detail., basic_html

Pituitary Gland - Cysts, multiple in a female F344/N rat from a chronic study. Higher magnification of Figure 5 shows the epithelium-lined cysts are present in the pars nervosa.

Authors and Reviewers

Authors

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

Amy Brix, DVM, PhD, DACVP
Senior Pathologist
Experimental Pathology Laboratories, 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

Deepa B. Rao, BVSc, MS, PhD, DABT, DACVP
NTP Pathologist (Contractor)
Integrated Laboratory Systems, Inc.
Research Triangle Park, NC