[788] PAX-8 Is a Specific Marker for Renal Neoplasms. Comparison with PAX-2, Renal Cell Carcinoma Marker Antigen (RCCM) and Kidney Specific Cadherin (KSP)
R Javed, QJ Zhai, SS Shen, B Krishnan, JY Ro, L Truong. The Methodist Hospital, Weil-Cornell Medical College, Houston, TX; Baylor College of Medicine, Houston, TX
Background: The current diagnostic immunomarkers for renal neoplasms (RNs) are limited. RCCM and KSP are terminally differentiated molecules expressed by proximal and distal tubules, respectively, and thus are markers only for subsets of RNs. PAX-2, a transcription factor promoting renal differentiation, is a sensitive RN marker. PAX-8 is another transcription factor that co-ordinates with PAX-2 in renal differentiation. Its role as a RN marker is not known.
Design: 51 RNs including 32 clear cell RCCs, 7 papillary RCCs, 7 chromophobe RCCs, and 5 oncocytomas were subjected to immunostain for PAX-8. Consecutive tumor tissue sections were also stained for PAX-2, RCCM, and KSP. The staining was quantified in terms of intensity and extent, and was compared among the four markers.
Results: PAX-8 expression with exclusive nuclear staining was successfully identified in formalin-fixed, paraffin-embedded tissue. In non-neoplastic kidney tissue, PAX-8 was identified a portion of normal collecting duct cells, and atrophic tubular cells regardless of origin. PAX-8 was also expressed in the vast majority of RNs (96%), regardless of histologic subtypes or differentiation, and was the most sensitive RN markers among those evaluated in table 1.
| PAX8 % | PAX2 (%) | RCCM (%) | KSC (%) | | Clear cell (n=32) | 100 | 91 | 81 | 34 | | Papillary (n=7) | 100 | 100 | 100 | 0 | | Chromophobe (n=7) | 86 | 86 | 0 | 100 | | Oncocytoma (n=5) | 80 | 100 | 0 | 80 | | Total (n=51) | 96 | 92 | 65 | 43 |
PAX-8, like PAX-2, was expressed by virtually all tumor cells in positive cases, in contrast to much smaller percentage of tumor cells expressed by RCCM or KSC.
Conclusions: PAX-8 can be reliably detected in archival tissue. Among the evaluated RN markers, it is the most sensitive. Since its staining is both widespread and independent of tumor grade and type of RNs, PAX-8 appears to be of important diagnostic utility for small tumor samples and determining renal origin of unknown primary tumors. Because PAX-8 constantly stains atrophic tubular cells regardless of origin, it may play an important pathogenic role in tubular atrophy.
Category: Genitourinary (including renal tumors)
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 140, Tuesday Afternoon
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