[902] The Diagnostic Utility of CAIX, TTF-1 and TGB Immunopanel in the Diagnosis of Metastatic Renal Cell Carcinoma to the Thyroid.

George Netto, Ashley Cimino-Mathews. The Johns Hopkins Hospital, Baltimore

Background: Clear cell renal cell carcinoma (ccRCC) may occasionally present with metastatic lesions. The thyroid is not an uncommon site for metastatic RCC, where such lesion could be misinterpreted as a clear cell change in adenomatoid nodules, follicular adenomas, or parathyroid glands. PAX8 is a transcription factor expressed by thyroid and renal-lineage cells. No prior study has evaluated the diagnostic utility of PAX8 and ccRCC marker carbonic anhydrase IX (CAIX) in this setting.
Design: Twelve cases of metastatic ccRCC to the thyroid, six parathyroid glands and parathyroid adenomas with clear cell change, six papillary thyroid carcinoma, five thyroid follicularadenomas and five thyroid adenomatoid nodules with clear cell change were retrieved from our archives. All cases were assessed by standard immunohistochemistry for thyroid transcription factor-1 (TTF-1; Cell Marque), thyroglobulin (TGB; Cell Marque), PAX8 (Pharmingen) and CAIX (Bond-Lecia). Extent and intensity of nuclear or cytoplasmic immunoexpression was assessed in each sample with any labeling considered a positive result.
Results: All metastatic ccRCC were positive for PAX8 (moderate to strong, patchy or diffuse) and CAIX (strong, diffuse), and were negative for TTF-1 and TGB. All primary thyroid lesions (normal thyroid, papillary thyroid carcinomas, follicular adenomas, and adenomatoid nodules) labeled strongly and diffusely for TTF-1, TGB and PAX8 and were negative for CAIX. Parathyroid tissue and adenomas were all negative for TTF-1, TBG, PAX8 and CAIX.


Conclusions: An immunoprofile of "TTF1(-)/TGB(-)/CAIX(+)" was 100% sensitive and specific for metastatic ccRCC to thyroid. The reverse profile "TTF1(+)/TGB(+)/CAIX(-)" supported a primary thyroid lesion. As expected, immunostaining with PAX8 is not helpful in distinguishing between metastatic ccRCC and primary thyroid lesions.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 114, Wednesday Morning

 

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