What is the histologic definition of sarcomatoid renal cell carcinoma (SRCC)?

Updated: Mar 11, 2019
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Sarcomatoid renal cell carcinoma (SRCC) is currently defined in the 2004 World Health Organization (WHO) classification of renal tumors as any histologic type of renal cell carcinoma (RCC) containing foci of high-grade malignant spindle cells. [1]

Many studies have defined a tumor as SRCC if even a small amount of sarcomatoid differentiation is present, [2, 3, 4, 5] whereas other studies have excluded tumors with a sarcomatoid component of less than 20% of the tumor volume [6] or less than one microscopic low-power (40x) field in size. [7]

However, some evidence exists of increased risk associated with sarcomatoid components comprising 5-10% of total tumor volume, [5, 7] indicating that even small amounts of sarcomatoid differentiation may be clinically relevant and should be included in the pathology report.

Focal spindling due to noncohesion of tumor cells is not considered to represent sarcomatoid differentiation. [7] Tumors with pure sarcomatoid morphology due to overgrowth of the RCC components are classified as SRCC if evidence of epithelial differentiation can be demonstrated through immunohistochemical or ultrastructural analysis.

In cases in which the histologic subtype of the RCC component is not recognizable, the tumor is designated as unclassified RCC with sarcomatoid differentiation. [1]

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