• All IHC stains will include a positive control tissue

• 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 carcinomas, 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

Submit a formalin-fixed, paraffin embedded tissue block

Formalin-fixed, paraffin embedded (FFPE) tissue block

FFPE tissue section mounted on a charged, unstained slide

Ambient (preferred)

• Unlabeled/mislabeled block
• Insufficient tissue
• Slides broken beyond repair

Immunohistochemical staining and microscopic examination

If requested, an interpretive report will be provided

Specifications

• 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

References

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).