Value of PAX 8 Immunostaining in Tumor Diagnosis: A Review and UpdateOrdóñez, Nelson G. MDAdvances in Anatomic Pathology: May 2012 - Volume 19 - Issue 3 - p 140–151 doi: 10.1097/PAP.0b013e318253465d Review Articles Abstract Author Information PAX 8 is a transcription factor involved in the regulation of organogenesis of the thyroid gland, kidney, and Müllerian system. Recent studies have shown that, among tumors, PAX 8 is commonly expressed in epithelial tumors of the thyroid and parathyroid glands, kidney, thymus, and female genital tract. Although PAX 8 expression has also been reported in certain neuroendocrine tumors, including well-differentiated pancreatic neuroendocrine tumors, and duodenal and rectal carcinoids, as well as in B-cell lymphomas, it has recently been shown that the PAX 8 positivity reported in these tumors was due to a cross-reactivity of the antibody used with the N-terminal region of PAX 6 and PAX 5, respectively. Owing to its restricted expression, PAX 8 has proved to be a useful immunohistochemical marker with a wide range of diagnostic applications in surgical pathology, some of which are briefly reviewed. The University of Texas M.D. Anderson Cancer Center, Houston, TX The author has no funding or conflicts of interest to disclose. Reprints: Nelson G. Ordóñez, MD, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030 (e-mail: firstname.lastname@example.org). © 2012 Lippincott Williams & Wilkins, Inc.