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Endocr Pathol. 2017 Dec;28(4):287-292. doi: 10.1007/s12022-017-9503-6.

Utility of Pit-1 Immunostaining in Distinguishing Pituitary Adenomas of Primitive Differentiation from Null Cell Adenomas.

Author information

1
Division of Neuropathology, Department of Pathology, University of California, 505 Parnassus Ave, Room M-551, Box 0102, San Francisco, CA, 94143, USA.
2
Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA.
3
Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA.
4
Trillium Health Partners, Mississauga, ON, Canada.
5
Division of Neuropathology, Department of Pathology, University of California, 505 Parnassus Ave, Room M-551, Box 0102, San Francisco, CA, 94143, USA. tarik.tihan@ucsf.edu.

Abstract

Pit-1 immunostaining is not routinely used in the characterization of pituitary adenomas, and its utility in distinguishing adenomas dedicated towards the lactotroph, somatotroph, and thyrotroph lineage from null cell adenomas warrants further evaluation. Pituitary adenomas that were negative for expression of a basic panel of hormonal markers (ACTH, prolactin, and growth hormone) were further evaluated for TSH, SF-1, and Pit-1 expression using a tissue microarray. Among the 147 identified pituitary adenomas that were negative for ACTH, prolactin, growth hormone, and TSH, expression of SF-1 was present in 68 cases (46%). Of the remaining 72 cases with sufficient tissue for further analysis, four were Pit-1 positive (6% of the adenomas negative for ACTH, prolactin, growth hormone, TSH, and SF-1); the remaining 68 were potentially null cell adenomas. Two of the Pit-1-positive adenomas displayed a paranuclear CAM 5.2 staining pattern suggestive of a sparsely granulated somatotroph adenoma; however, only one case contained fibrous bodies within a majority of the adenoma cells. Our data suggests that Pit-1 can be utilized as a second tier immunostain in cases of clinically non-functioning adenomas that are immunonegative for ACTH, prolactin, growth hormone, TSH, and SF-1 in order to further segregate rare cases of Pit-1-positive adenomas from null cell adenomas. Pit-1 immunostaining can recognize rare cases of sparsely granulated somatotroph adenomas that appear immunonegative for growth hormone, as well as rare cases of other Pit-1-positive adenomas that are negative for Pit-1 lineage hormones. Overall, pituitary adenomas of the Pit-1 lineage that do not produce prolactin, growth hormone, or TSH are rare, with only four cases identified in the current study.

KEYWORDS:

Clinically non-functioning pituitary adenoma; Null cell adenoma; Pit-1; Pituitary adenoma; SF-1; Silent adenoma; Sparsely granulated somatotroph adenoma; Transcription factors

PMID:
28994039
DOI:
10.1007/s12022-017-9503-6
[Indexed for MEDLINE]

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