Immunohistochemical expression of PAX8, PAX2, and cytokeratin in melanomas. (13th May 2021)

• Record Type: Journal Article
• Authors: Plotzke, Jaclyn M.; Zhao, Raymond; Hrycaj, Steven M.; Harms, Paul W.; Mehra, Rohit; Chan, May P.
• Is Part Of: Journal of cutaneous pathology. Volume 48:Number 10(2021)
• Page Start: 1246
• Page End: 1251
• Publication Date: 2021-05-13
• Subjects: cytokeratin -- melanoma -- MiTF -- PAX2 -- PAX8 -- renal cell carcinoma; Skin -- Diseases -- Periodicals; Dermatology -- Periodicals; 616
• DOI: 10.1111/cup.14041
• Languages: English
• ISSNs: 0303-6987

Abstract

Abstract: Background: Deviations from the classic melanocytic immunophenotype in melanoma can present a diagnostic challenge. PAX8 and PAX2 are common markers for renal or Müllerian differentiation. While most PAX8+ or PAX2+ carcinomas are seldom confused with melanoma, some cases may show a more ambiguous immunophenotype, especially when MiTF family altered renal cell carcinoma (MiTF‐RCC) is in the differential diagnosis. Neither PAX8 nor PAX2 expression has been reported in melanoma to date. We aimed to better characterize PAX8, PAX2, and cytokeratin immunoreactivity in a large series of melanomas. Methods: Tissue microarrays consisting of 263 melanomas were immunostained for PAX8, PAX2, and cytokeratin and graded by an h‐score. Results: PAX8 expression was seen in 7.9% of melanomas and was significantly associated with spindle cytomorphology. PAX2 was positive in one (0.4%) melanoma. Cytokeratin positivity was seen in three (1.2%) cases and was associated with metastases. Conclusions: PAX8 is expressed in a subset of melanomas and may be strong/extensive. As PAX8 positivity does not exclude a diagnosis of melanoma, it should be used in conjunction with other immunohistochemical markers, such as cytokeratin and PAX2, when melanoma, MiTF‐RCC, and other PAX8+ tumors are in the differential diagnosis.