Which immunohistochemical findings are characteristic of sarcomatoid renal cell carcinoma (SRCC)?

Updated: Mar 11, 2019
  • Author: Ronald J Cohen, MB, BCh, PhD, FRCPA, FFPATH; Chief Editor: Liang Cheng, MD  more...
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Immunoreactivity for epithelial markers is common in the sarcomatoid components of SRCC, providing evidence of their epithelial derivation. Positive staining in sarcomatoid areas is most frequently obtained with cytokeratin cocktail AE1/AE3 (33-94%) and epithelial membrane antigen (50-55%), while the intermediate filament vimentin is expressed in 56-100% of cases. Despite the spindle cell morphology, immunoreactivity for muscle-specific actin is only seen in 22% of cases, and staining for desmin is almost always negative. [17, 18, 38, 39]

As expected with transformation, sarcomatoid tumor components tend to lose the staining patterns that are characteristic of their RCC components. Sarcomatoid regions of chromophobe SRCC show only patchy staining with Hales colloidal iron and are negative for expression of parvalbumin and cytokeratin 7. [40] Similarly, sarcomatoid regions of papillary SRCC show significantly reduced expression of AMACR compared with the RCC components. [41]

However, sarcomatoid components of SRCC have significantly higher expression of the Ki-67 nuclear proliferation antigen compared with the RCC components, consistent with the aggressive behavior associated with sarcomatoid differentiation. [6]

SRCC with a predominant sarcomatoid component can be difficult to distinguish from other spindle cell neoplasms that occur in the kidney. Distinction from true smooth muscle tumors such as leiomyoma or leiomyosarcoma is aided by extensive sampling to detect an epithelial component in SRCC or by confirmation of epithelial derivation with immunohistochemical or ultrastructural analysis. Furthermore, immunostains for desmin are positive for leiomyoma and leiomyosarcoma, but they are negative for SRCC. [42]

Primary renal sarcomas may have unique cytogenetics features that serve to distinguish them from SRCC, as with the characteristic t(X:18) (p11.2-q11.2) translocation demonstrated in a primary renal synovial sarcoma. [43] Immunostains for HMB-45 or Melan A distinguish SRCC from smooth-muscle-predominant angiomyolipomas with hypercellularity and nuclear pleomorphism, which have positive immunoreactivity for these markers. [42, 44]

Similarly, immunostains for CD34 distinguish SRCC from solitary fibrous tumor and hemangiopericytoma, which have positive reactivity for these markers. [42]

However, urothelial or transitional cell carcinoma (TCC) that has undergone extensive sarcomatoid change can resemble SRCC in both morphology and immunohistochemical profile. Distinction between these tumor types is possible only by identifying components of usual TCC or RCC, respectively. [45]

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