Sarcomatoid renal cell carcinoma is a highly aggressive tumor. It is not a distinct histologic entity as it can be found in any subtypes of renal cell carcinoma. Recent molecular and genetic evidence suggest that sarcomatoid component is transformed from a common progenitor of the associated renal cell carcinoma, and the TP53 gene plays a pivotal role in this process. The presence of sarcomatoid carcinoma indicates poor prognosis, which also correlates with the amount of the sarcomatoid component. Therefore, the presence and quantity of sarcomatoid component should be reflected in pathology reports. However, pathology reporting seems to vary among laboratories prompting the need for a unified reporting system. We propose a pathology reporting system similar to that of transformed follicular lymphoma that is consistent with the molecular pathogenesis to ensure uniform reporting.