PAX8 reliably distinguishes ovarian serous tumors from malignant mesothelioma

Am J Surg Pathol. 2010 May;34(5):627-35. doi: 10.1097/PAS.0b013e3181da7687.


Ovarian serous neoplasms can have morphologic overlap with malignant mesothelioma. The distinction is clinically important, yet most studies have failed to identify immunostains that reliably distinguish these 2 tumor types. Recently, transcription factor PAX8 was shown to be a sensitive and relatively specific marker for Müllerian tumors. In addition, some studies suggest that h-caldesmon is sensitive and specific for mesothelioma when compared with serous ovarian tumors. The goal of this study was to evaluate whether PAX8 and h-caldesmon expression can successfully distinguish mesothelioma from serous ovarian tumors. Immunohistochemistry was carried out using PAX8 and h-caldesmon antibodies on archival tissue from 254 ovarian serous tumors and 50 mesothelial tumors. Nuclear and cytoplasmic immunoreactivity were considered positive for PAX8 and h-caldesmon, respectively. PAX8 staining was present in 99% of high-grade serous ovarian carcinomas and all (100%) low-grade ovarian carcinomas and serous borderline tumors; however, only 74% of these cases (188/254) were diffusely positive in more than 50% of tumors cells, and intensity ranged from strong to weak. None of the pleural malignant mesotheliomas were reactive with PAX8. However, 2/23 (9%) peritoneal malignant mesotheliomas showed focal and/or weak staining for PAX8; the remaining cases were negative. Two well-differentiated papillary mesotheliomas and 1 multicystic mesothelioma each showed some staining for PAX8. h-caldesmon was negative in all serous neoplasms and all mesothelial neoplasms, except 1 pleural malignant mesothelioma which showed patchy immunoreactivity. Strong PAX8 staining is highly specific (P<0.00001) for ovarian serous tumors when compared with malignant mesotheliomas of the peritoneum and pleura. The presence of weak staining for PAX8 in the 3 "noninvasive" mesotheliomas questions the use for PAX8 in this differential diagnosis. On the basis of this study, h-caldesmon is not a useful marker for mesothelioma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers, Tumor / metabolism
  • Calmodulin-Binding Proteins / metabolism
  • Cystadenocarcinoma, Serous / diagnosis*
  • Cystadenocarcinoma, Serous / metabolism
  • Diagnosis, Differential
  • Female
  • Fluorescent Antibody Technique, Direct
  • Humans
  • Immunoenzyme Techniques
  • Mesothelioma / diagnosis*
  • Mesothelioma / metabolism
  • Ovarian Neoplasms / diagnosis*
  • Ovarian Neoplasms / metabolism
  • PAX8 Transcription Factor
  • Paired Box Transcription Factors / metabolism*
  • Peritoneal Neoplasms / diagnosis*
  • Peritoneal Neoplasms / metabolism
  • Pleural Neoplasms / diagnosis*
  • Pleural Neoplasms / metabolism


  • Biomarkers, Tumor
  • Calmodulin-Binding Proteins
  • PAX8 Transcription Factor
  • PAX8 protein, human
  • Paired Box Transcription Factors