Allina Health Laboratory a part of Abbott Northwestern Hospital



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Test Name:PAX8 by IHC
Test Number:12376 - Technical only; 12379 - Technical & Interpretation
Collect:Formalin-fixed, paraffin embedded (FFPE) tissue block
Container:FFPE tissue block
Processing:Submit processed tissue block or tissue section mounted on a charged, unstained slide
Transport/Stability:Ambient (preferred)
Alternate Names:IHC
Performing Lab:AHL - Immunohistochemistry
Days Set Up:Mo - Fr
Expected TAT:1 - 2 days
Ref. Ranges:If requested, an interpretive report will be provided
All IHC stains will include a positive control tissue
Processing Details:

  • PAX8 is a member of the PAX family of transcription factors that are active in thyroid development
  • PAX8 expression is seen in thyroid, non-ciliated mucosal cells of fallopian tubes, ovarian inclusion cysts, and in renal tubular cells and associated tumors
  • PAX8 positivity can be seen in B-cell lymphomas, likely due to cross reactivity with PAX5

Staining pattern:
  • Nuclear
  • PAX8 is expressed in ovarian serous (99%), endometrioid (98%), and clear cell carcinomas (78%) (and only very rarely in mucinous ovarian tumors), and cervical carcinomas (91%)
  • PAX8 is present in 90-98% of clear cell renal cell carcinomas, 90% of papillary renal cell carciomas, and 81-95 % of oncocytomas
  • PAX8 is expressed in thyroid neoplasms (91%)
  • No (or focal weak) expression for PAX8 is seen in lung, breast, and non-GYN carcinomas
  • Thymic carcinomas and thymomas may show moderate staining with PAX8
  • PAX8 is useful in a panel differentiating peritoneal mesothelioma from papillary serous
  • PAX8 can be used to discriminate GYN tumors from breast tumors
  1. Laury AR et al: A Comprehensive Analysis of PAX8 Expression in Human Epithelial Tumors Am J Surg Pathol 2011;35:816-826).
  2. Morgan EA at al: PAX8 and PAX5 are differentially expressed in B-cell and T-cell lymphomas. Histopathology 2013, 62, 406-413.
  3. Moretti L at al: N-terminal PAX8 polyclonal antibody shows cross-reactivity with N-terminal region of PAX5 and is responsible for reports of PAX8 positivity in malignant lymphomas. Modern Pathology 2012, 25, 231-236.
  4. Ordonez NG: Value of PAX 8 Immunostaining in Tumor Diagnosis: A Review and Update. Adv Anat Pathol 2012;19:140-151).
Method:Immunohistochemical staining
Microscopic examination
CPT Codes:88342 - 1st stain
88341 - each additional stain
Date Created:08/07/2017
Revised Date:10/19/2018