[874] Comparison of PAX-2 and PAX-8 Expression in Primary Neoplastic and Metastatic Tumors of Wolffian Duct and Mullerian Origin.

Annisa Lewis, Steve Shen, Jae Ro, Alberto Ayala, Luan Truong. Methodist Hospital, Houston, TX

Background: PAX-2 and PAX-8 are homologous and complementary members of the pair box gene family. They are known to control the development of organs derived from the Wolffian and Mullerian ducts. Individual studies suggest a similar expression of PAX-2 and PAX-8 in normal and neoplastic tissue. However, direct comparison of their tissue expression, which may imply both biologic and diagnostic importance, is not available.
Design: Immunostaining for PAX-2 and PAX-8 on consecutive formalin-fixed, paraffin embedded tissue sections from samples of non-neoplastic tissue (n=202), primary tumors (n=500), and metastatic tumors (n=275) was performed. Staining frequency (% of cases), extent (% of stained cells), and intensity (0-3+) were compared.
Results: For non-neoplatic tissue, virtually identical (constant, strong, diffuse) expression of PAX-2 and PAX-8 was noted in epithelial cells of uterine cervix, endometrium, fallopian tube, seminal vesicle, testicular efferent duct, and distal renal tubules. PAX-8, but not PAX-2, was present in all thyroid tissue samples and 85 % of pancreatic islet cells. For primary neoplasms, PAX-2 and PAX-8 were expressed in renal cell carcinoma (RCC) and tumors of Mullerian origin. Among RCC (n=166), expression was 63.25% and 87.35% of tumors, extent of staining was 56.19% and 71.99% of tumor cells, and the intensity scores were 1.49 and 1.8 for Pax-2 and Pax-8 respectively. Among tumors of Mullerian origin, the expression of Pax-2 and Pax-8 was: 43.40% and 90.56% of tumors, staining extent 24.47 % and 85.88% of tumor cells, and intensity scores 1.1 and 2.57, respectively. PAX-8, but not PAX-2, was noted in all 67 papillary or folicular thyroid neoplasms and 75% of 15 well-differentiated pancreatic neuroendocrine tumors. Focal weak staining for both PAX-2 and PAX-8 was noted in a few parathyroid lesions. The stronger and more extensive PAX-8 expression noted in primary tumors was also noted for metastases (2 and 2.59; mean intensity scores, Pax-2 and Pax-8, respectively).
Conclusions: There is significant overlapping expression of PAX-2 and PAX-8 in both normal and neoplastic tissue, in keeping with their similar genetic ontogeny. However, remarkable differences are also noted including more expression of PAX-8 over PAX-2 for both primary and metastatic RCC and Mullerian tumors, and frequent PAX-8, but not PAX-2, expression in other tumors including thyroid follicular tumors and pancreatic neuroendocrime tumors. PAX-8 provides better diagnostic yield than PAX-2 and perhaps may supersede PAX-2 in selecting a diagnostic panel.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 137, Wednesday Afternoon


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