[808] Immunohistochemistical Profile of Sarcomatoid Renal Cell Carcinoma

A Chang, E Montgomery, JI Epstein. The Johns Hopkins Hospital, Baltimore

Background: Sarcomatoid renal cell carcinoma (RCC) has a poor prognosis. Its diagnosis as a primary renal tumor may be difficult, especially when morphologic evidence of epithelial differentiation is limited or entirely absent. Only limited immunohistochemical (IHC) studies using antibodies that more specifically label RCC have addressed sarcomatoid RCC.
Design: TMAs were made from 46 primary sarcomatoid RCCS (including 18 cases with a carcinomatous component), including 3 lymph node and 1 intestinal metastases. TMAs included sarcomatoid and carcinoma areas, if present. IHC for PAX8, PAX2, RCC, and CD10 was performed.
Results: In areas of sarcomatoid morphology, PAX8 was the most sensitive marker.

(+) staining in sarcomatoid areas36/46 (78%), 10 focal25/46 (54%), 19 focal4/46 (6%), 2 focal33/46 (72%), 8 focal

Of 18 cases with epithelial components, 10 (55%) were clear cell, 2 (11%) were chromophobe, 2 cases (11%) were papillary, and 4 (22%) unclassified. Histology of the non-sarcomatoid areas did not correlate with staining characteristics. The IHC of cases with both carcinomatous and sarcomatoid areas is shown in the table below.

(+) staining in carcinomatous areas14/18 (78%)10/18 (56%)9/18 (50%)14/18 (78%)
retention of staining in sarcomatous areas12/14 (86%)9/10 (90%)3/9 (33%)11/14 (79%)

All 4 primaries and their metastases were positive for PAX2. The primaries associated with the intestinal and 2 of 3 cases lymph node metastases were positive for PAX8 and CD10, which were retained within the metastatic sites. All 4 primaries and their metastases were negative for RCC.
Conclusions: PAX8 was the most sensitive marker for sarcomatoid RCC. CD10 was a fairly sensitive marker of sarcomatoid RCC, however, is expressed in a variety of non-renal tissues, while PAX 8, a nephric-lineage transcription factor, is more specific for RCC. PAX2, while being closely related to PAX8, was less sensitive than both PAX8 and CD10, and PAX2 showed more background non-specific staining. RCC was the least sensitive marker examined. Concerning metastatic lesions, while our sample size was small, staining for PAX8, PAX2, and CD10, if present in the primary renal lesion, was retained in the metastatic site. We are in the process of labeling a TMA composed of various sarcomas for PAX8 to assess its specificity for sarcomatoid RCC when presented with a malignant spindle cell tumor and no known primary.
Category: Genitourinary (including renal tumors)

Tuesday, March 23, 2010 1:30 PM

Platform Session: Section A, Tuesday Afternoon


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