[1022] PAX8 Mouse Monoclonal Antibody: A Comprehensive and Comparative Study on Normal and Neoplastic Tissues

David Tacha, Ding Zhou, Ryan Bremer, Liang Cheng. Biocare Medical, Concord, CA; Indiana School of Medicine, Indianapolis, IN

Background: PAX8 rabbit polyclonal (P) antibody is expressed in a high percentage of kidney and ovarian cancers; however, PAX8 (P) recognize B-cells, pancreatic cancers, carcinoids and some soft tissue tumors. B-cell expression can be especially problematic in lymph nodes when identifying tumors of unknown origin or distinguishing lymph node metastases. A new mouse monoclonal hybridoma PAX8 (M) antibody [BC12] has been developed for IHC. In this study PAX8 (M) was tested for specificity and sensitivity in over 1200 cases of normal and neoplastic tissues. In particular, PAX8 (M) vs. PAX8 (P) was compared in (RCC) and ovarian cancers.
Design: Formalin-fixed paraffin embedded whole tissues and TMAs were constructed from archival tissues. Patient information included age, sex, diagnosis, grade and stage. Tissue was processed in the usual manner and immunohistochemistry (IHC) was performed using polymer detection. Cases were considered positive if nuclear staining was observed in ≥5% of the cells.
Results: PAX8 (M), exclusively expressed in nuclei, demonstrated equal or superior sensitivity in both renal cell and ovarian carcinomas (Table 1 and 2). PAX8 (M) also demonstrated high sensitivity in endometrioid and thyroid cancers, 67.5% and 60.7% respectively. Low sensitivity of PAX8 (M) was observed in cervical and bladder cancers, 2.5% and 1.4% respectively. All other cancers evaluated, including lung, breast, prostate, stomach, liver, soft tissue, pancreas, testis, brain, colon, melanoma, lymphoma, adrenal, pituitary and rectal were negative. In normal tissue, PAX8 (P) stained lymph nodes, pancreas, and neuroendocrine cells of stomach and colon (confirmed by chromogranin). Conversely, PAX8 (M) was negative in each of these tissues.

Table 1: RCC
 PAX8 (M) PAX8 (P) 
DiagnosisCases (+)% (+)Cases (+)% (+)
Clear cell RCC154/17884.6%148/17883.1%
Papillary RCC13/1492.9%12/1485.7%

Table 2: Ovarian Cancer
 PAX8 (M) PAX8 (P) 
DiagnosisCases (+)% (+)Cases (+)% (+)
Serous cystadenocarcinoma53/5891.4%53/5891.4%
Endometrioid adenocarcinoma27/3772.9%25/3767.6%

Conclusions: These results demonstrate that PAX8 (M) is a highly specific and sensitive marker for renal ovarian and thyroid cancers. Importantly, PAX (M) does not stain B-cells, and does not recognize epitopes of pancreatic origin or neuroendocrine cells in stomach and colon.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 156, Tuesday Morning


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