Pathology Outlines

Stains
PAX8

Author: Nat Pernick, M.D. (see Authors page)

Revised: 14 February 2017, last major update November 2011

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: PAX8

Table of Contents

Cite this page: PAX8. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/stainspax8.html. Accessed July 12th, 2017.

Definition / general

Also called Paired box 8
Discovered in 1990 (Development 1990;110:643)
Paired domains are composed of two helix-turn-helix subdomains
- The N-terminal subdomain and the C-terminal subdomain, both of which can bind DNA independently (Cell 1995;80:639)
Structurally similar to PAX2 and PAX5

Pathophysiology

Gene is at 2p13 (NCBI - PAX8)
Transcription factor critical for development of eye, thyroid, urinary and reproductive organs
Associated with tumors of thyroid gland, kidney / upper urinary tract and Müllerian system
Mutations associated with congenital hypothyroidism and hypoplasia (J Clin Endocrinol Metab 2001;86:3962, J Clin Endocrinol Metab 2001;86:234)
PAX8-PPARgamma rearrangement in follicular thyroid carcinoma (53%, Am J Surg Pathol 2002;26:1016), follicular adenoma (8%) and follicular variant of papillary thyroid carcinoma (38%, J Clin Endocrinol Metab 2006;91:213)

Interpretation

Nuclear staining
Actually negative in B cell lymphomas, but reported positive due to cross reactivity between the N-terminal regions of PAX8 and PAX5, due to the high sequence homology of these two regions (Mod Pathol 2012;25:231)

Uses by pathologists

Differentiate PAX8+ primary or metastatic tumors (kidney, Mullerian [but not mucinous, Am J Surg Pathol 2011;35:1837], thymic, thyroid) from PAX8- tumors (adrenal, breast, GI [most], lung, prostate, Am J Surg Pathol 2011;35:816)
Differentiate prostatic mesonephric remnant hyperplasia (PAX8+) from prostatic adenocarcinoma (PAX8-, Am J Surg Pathol 2011;35:1054)
Differentiate metastatic clear cell renal cell carcinoma (PAX2+ or PAX8+ / inhibinA neg) from hemangioblastoma (PAX2-, PAX8-, inhibin A+, Am J Surg Pathol 2011;35:262)
Differentiate endosalpingiosis in axillary lymph nodes (PAX8+ / WT1+) from metastatic breast carcinoma (PAX8-, WT1-, Am J Surg Pathol 2010;34:1211)
Differentiate renal collecting duct carcinoma (PAX8+ / p63-) from urothelial carcinoma of upper urinary tract (PAX8- / p63+, Am J Surg Pathol 2010;34:965)
Differentiate thyroid anaplastic carcinoma (PAX8+) from head and neck squamous cell carcinoma (PAX8-, Hum Pathol 2011;42:1873)
Determine primary site of invasive micropapillary carcinomas as part of panel (Am J Surg Pathol 2009;33:1037)
Marker of nephrogenic adenoma
Determine renal tubular origin of various disease processes (Am J Surg Pathol 2011;35:1264)

Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Andrey Bychkov, M.D., Ph.D.:

Expression by thyroid follicular cells

Papillary thyroid carcinoma, PAX8

Images hosted on other servers:

Kidney

Normal adult kidney

Renal epithelial tumors

Thyroid carcinomas

Urothelial carcinoma

Positive staining - normal

Epithelium of endocervix, endometrium, fallopian tubes, kidney (glomerular parietal epithelial cells, renal collecting ductal cells, atrophic renal tubular epithelial cells, Mod Pathol 2011;24:751), thyroid
Ovarian inclusion cysts, pancreatic islet cells
Epithelium of male genital tract from rete testis to ejaculatory duct, but not prostate

Positive staining - disease

Endometrial polyp, endometriosis, endosalpingiosis, paratubal cyst, prostatic mesonephric remnant hyperplasia
Bladder clear cell adenocarcinoma, endometrial adenocarcinoma
Ovarian carcinoma, except mucinous types (Am J Surg Pathol 2008;32:1566)
Renal cell carcinoma (90%, Mod Pathol 2009;22:1218), including Xp11 translocation subtype (Am J Surg Pathol 2010;34:1295), renal oncocytoma (81%), nephrogenic adenoma (Am J Surg Pathol 2008;32:1380), nephroblastoma, renal cell carcinoma
Seminoma, thymic carcinoma, thymoma types A and B (Am J Surg Pathol 2011;35:1305)
Thyroid anaplastic carcinoma (Mod Pathol 2008;21:192) and other thyroid tumors (91%, Am J Surg Pathol 2011;35:816)
Carcinoid tumors: gastric / duodenal (100%), rectal (85%), appendix (21%), gastric (20%), but not ileal, lung (Am J Surg Pathol 2010;34:723) or renal (Hum Pathol 2011;42:1554)
Neuroendocrine tumors: duodenal (75%), pancreas (67%, Am J Surg Pathol 2010;34:723), rectal (29%), gastric (10%), appendiceal (9%), but not ileal or lung (Mod Pathol 2011;24:412)

Negative staining

Normal epithelium of bladder, lung, parathyroid (Am J Surg Pathol 2011;35:757) and prostate
Normal testis: seminiferous tubules, interstitium
Carcinomas: adrenal gland, bile duct, breast (Am J Clin Pathol 2011;136:428), gastric, GE junction, lung, pancreas, prostate, urothelial (also urothelial adenocarcinoma and squamous carcinoma, Appl Immunohistochem Mol Morphol 2011;19:293)
Adenomatoid tumor, Leydig and Sertoli cell tumors, germ cell tumors (Am J Surg Pathol 2011;35:1473), mesothelioma (Am J Surg Pathol 2010;34:627)
B cells and B cell lymphomas (reported positive due to cross reactivity with PAX5 due to high sequence homology)