PAX8 and PAX2 immunostaining facilitates the diagnosis of primary epithelial neoplasms of the male genital tract

Our plain-English summary of PAX8 and PAX2 immunostaining facilitates the diagnosis of primary epithelial neoplasms of the male genital tract, by G.X. Tong, L. Memeo, C. Colarossi, et al (The American Journal of Surgical Pathology, 2011).

The study

• Authors: G.X. Tong, L. Memeo, C. Colarossi, D. Hamele-Bena, C. Magi-Galluzzi, M. Zhou, S.M. Lagana, L. Harik, J.M. Oliver-Krasinski, M. Mansukhani, L. Falcone, H. Hibshoosh, K. O'Toole
• Journal: The American Journal of Surgical Pathology
• Published: 2011;35(10):1473-83
• Type of article: Case report
• Cited by: 44 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

PAX8 and PAX2 are cell-lineage-specific transcription factors that are essential for the development of Wolffian and Müllerian ducts and have recently emerged as specific diagnostic markers for tumors of renal or Müllerian origin. Little is known about their expression in the Wolffian duct-derived human male genital tract. We report our findings of PAX8 and PAX2 expression in the epithelium of the normal male genital tract and in epithelial tumors derived therefrom using immunohistochemistry (IHC). We found that PAX8 and PAX2 were expressed in the epithelium of the male genital tract from the rete testis to the ejaculatory duct. Rare glands in the prostatic central zone, a tissue of purported Wolffian duct origin, were focally positive for PAX2, but no PAX8 was detected in this area, a finding that may warrant further study. We found diffuse expression of PAX8 and PAX2 in 1 case each of serous cystadenoma of the epididymis, carcinoma of the rete testis, Wolffian adnexal tumor of the seminal vesicle, and endometrioid carcinoma of the seminal vesicle. Neither PAX8 nor PAX2 was detected in the seminiferous tubules and interstitium of the normal testis, nor in Leydig cell tumors (n=6), Sertoli cell tumors (n=2), or 48 of 49 germ cell tumors. One pediatric yolk sac tumor showed focal and weak staining for PAX8. Tumors of mesothelial origin, that is, adenomatoid tumors (n=3) and peritoneal malignant mesotheliomas (n=37) in men, were negative for PAX2 and PAX8. Neither PAX2 nor PAX8 was present in other areas of the prostate. Expression of PAX8 and PAX2 in these primary epithelial neoplasms of the male genital tract is due to their histogenetic relationship with Wolffian or Müllerian ducts. PAX8 and PAX2 IHC may facilitate the diagnosis of these tumors and should be included in the differential diagnostic IHC panel.

In plain English

This laboratory study tested whether two proteins, PAX8 and PAX2, appear on immunostaining (a tissue-staining method) of the male genital tract and its tumors. The authors stained normal genital tract tissue from 5 cases, 10 prostates, 4 primary epithelial tumors of the male genital tract, 57 testicular tumors, 37 peritoneal malignant mesotheliomas from men, 3 adenomatoid tumors and 4 mesonephric remnants. Both proteins appeared in the lining cells of the male genital tract from the rete testis to the ejaculatory duct, but not in testicular tubules. In the prostate, weak PAX2 staining appeared in rare central zone glands in 2 of 10 cases. No prostatic gland showed PAX8, though ejaculatory ducts and mesonephric remnants in the prostate stained for both proteins. All 4 primary epithelial tumors stained, though the rete testis carcinoma was only focally and weakly positive for PAX2. Apart from focal, weak PAX8 staining in one childhood yolk sac tumor, testicular tumors were negative, as were all adenomatoid tumors and peritoneal mesotheliomas. The study did not examine asbestos exposure. The authors concluded this staining may help diagnose these uncommon tumors.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Immunohistochemistry (tissue staining) study of pathology specimens and tissue microarrays, including descriptions of 4 individual tumor cases
• Who was studied: Normal male genital tract tissue (n = 5); prostates with central zones (n = 10); 4 primary epithelial tumors of the male genital tract; 57 testicular germ cell and sex cord-stromal tumors; 37 male peritoneal malignant mesotheliomas; 3 adenomatoid tumors (2 from women, 1 from the epididymis); 4 mesonephric remnants. The article does not state where or when the specimens were collected.
• Exposure: Not applicable. No asbestos or other exposure was studied. The tissues were stained for the PAX8 and PAX2 proteins.
• Main results:
  • In normal tissue, PAX8 and PAX2 were found in the epithelium of the male genital tract from the rete ductuli through the efferent ducts, epididymis, vas deferens and seminal vesicles to the ejaculatory ducts. Staining was limited to epithelial cells.
  • Prostate central zone: focal, weak PAX2 staining appeared in rare glands in 2 of the 10 prostates. No PAX8 was found in any central zone gland.
  • The ejaculatory ducts and mesonephric remnants located within the prostate were positive for both PAX2 and PAX8.
  • All 4 primary epithelial tumors of the male genital tract expressed PAX8 and PAX2: serous cystadenoma of the epididymis, adenocarcinoma of the rete testis, Wolffian adnexal tumor of the seminal vesicle, and endometrioid adenocarcinoma of the seminal vesicle.
  • The adenocarcinoma of the rete testis (in a 71-year-old man) was strongly positive for PAX8 but only focally and weakly positive for PAX2.
  • The testicular tumors were 32 seminomas, 13 embryonal carcinomas, 3 yolk sac tumors, 1 choriocarcinoma, 6 Leydig cell tumors and 2 Sertoli cell tumors. None showed PAX8 or PAX2, except one pediatric yolk sac tumor with focal, weak PAX8 staining.
  • None of the 3 adenomatoid tumors and none of the 37 peritoneal malignant mesotheliomas in men stained for PAX8 or PAX2.
• The authors' conclusion: The authors concluded that PAX8 and PAX2 staining may help in diagnosing these uncommon primary epithelial tumors of the male urogenital tract.
• Limitations the authors state:
  • The authors had no cases of malignant mesothelioma of the tunica albuginea or other paratesticular areas. Their expectation that such tumors would be negative is a postulate, not a tested finding.
  • The authors caution that some lymphocytes can stain for PAX2 or PAX8 and could be mistaken for tumor cells.

Topics

Medical terms in this study, explained in our Lexicon: Neoplasm, Epithelium, Immunohistochemistry, Rete Testis, Epididymis, Carcinoma, Tubule, Germ Cell Tumor.

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• Value of PAX8, PAX2, napsin A, carbonic anhydrase IX, and claudin-4 immunostaining in distinguishing pleural epithelioid mesothelioma from metastatic renal cell carcinoma — N.G. Ordóñez (2013)
• Palliation of male genital cancers — C.J. Shukla, M. Shabbir, et al. (2010)
• PAX8 reliably distinguishes ovarian serous tumors from malignant mesothelioma — A.R. Laury, J.L. Hornick, et al. (2010)
• Cytological differential diagnosis among adenocarcinoma, epithelial mesothelioma, and reactive mesothelial cells in serous effusions by immunocytochemistry — X.Y. Su, G.D. Li, et al. (2011)

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