PAX8

PAX8 is a nuclear transcription factor belonging to the paired‑box (PAX) family and functions as a key regulator of organogenesis involving the thyroid, kidney, and Müllerian‑derived organs. It is nuclear marker with strong expression in epithelial neoplasms of thyroid, thymic, ovarian, endometrial, endocervical, fallopian tube, and renal origin, with additional variable expression in selected CNS tumours and sarcomas. Both polyclonal and monoclonal PAX8 antibodies exist, though polyclonal antibodies may cross‑react with PAX5 and PAX6, whereas monoclonal antibodies are more specific. Nuclear staining must be strong to be considered positive. PAX8 is widely for identifying tumours of Müllerian, thyroid, or renal origin(1).

Recommended Controls

Criteria for acceptable staining is a nuclear staining reaction. The recommended positive control to use for a PAX8 stain is either fallopian tube or kidney, while tonsil can be used as a negative control, where there should not be any staining in the squamous epithelial cells. Ovarian cancer will be diffusely positive, which is a high expressor.

Expected staining pattern

Fallopian tube

Ovarian tumour

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.