• Sarcoma-like histology in a renal tumor is not a distinct entity but a pathway of transformation (dedifferentiation) in subtypes of renal cell carcinoma (RCC) (Cancer 2005;104:1195)
• 1 - 5% of RCC have a sarcomatoid component (Am J Surg Pathol 1997;21:1188, Ann Diagn Pathol 2003;7:296)
• Presence of even a focal sarcomatoid component is associated with a worse prognosis (Am J Surg Pathol 2001;25:275)

• Represents RCC loss of epithelial phenotype and gain of mesenchymal characteristics, epithelial-mesenchymal transition, a more aggressive phenotype with increased risk for local spread and high metastatic potential (Cancer 2005;104:1195)
• May be diffuse or focal; even focal sarcomatoid component is important and associated with a poor prognosis
• When the background RCC subtype is recognizable, it should be specified under histologic type
• If no underlying RCC subtype is detected, then tumor with pure sarcomatoid differentiation falls into the category of unclassified RCC and should be distinguished from sarcoma
• Sarcomatoid morphology is categorized as WHO / ISUP grade 4 (CAP: Protocol for the Examination of Specimens from Patients with Invasive Carcinoma of Renal Tubular Origin [Accessed 29 August 2018])

• Also called spindle cell carcinoma or carcinosarcoma

• Mean age 60 years, 60% men, usually stage 3 or 4
• Aggressive with median survival of 4 - 19 months; 5 year survival 22%, 10 year survival 13% (vs. 79%/76% without sarcomatoid differentiation) (J Urol 2002;167:65) (Oncologist 2012;17:46, Urol Oncol 2015;33:427)
• Metastases to lung and bones are common

• 90% symptomatic with pain, gross hematuria, weight loss
• Presentation with advanced disease and metastasis common

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• Percentage of sarcomatoid component may be prognostic, currently optional to report percentage:
  • ≥ 50% yielded poor prognosis (Am J Surg Pathol 2004;28:435)
  • > 40% least likely to be alive at 1 year (Urol Oncol 2015;33:427)
  • > 10% had higher risk of death (Urol Oncol 2015;33:427)

• Nephrectomy
• Combination chemotherapy regimens such as doxorubicin plus gemcitabine
• Interferon or interleukin-2 immunotherapy (J Urol 2002;167:65)

Contributed by Daniel Anderson, M.D., M.B.A.


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• Clear cell carcinoma with early spindle cell change: stroma is not malignant (Hum Pathol 2007;38:1372)
• Primary renal sarcoma: usually leiomyosarcoma; primary renal sarcomas have no epithelial component after careful sampling
• Primary retroperitoneal soft tissue sarcoma: usually liposarcoma; no epithelial component after careful sampling

A chromophobe renal cell carcinoma is well sampled and an area is seen in the above image. What is the value of documenting the percentage of this component?


1. Associated with lower stage
2. The finding has a worse prognosis
3. The finding has an improved prognosis
4. There is no prognostic implication

B. Worse prognosis. Those with higher percentages of sarcomatoid differentiation in a renal cell carcinoma have a worse prognosis including distant metastases at time of nephrectomy and higher overall mortality than if no sarcomatoid component was identified.

Reference: Kidney tumor - Sarcomatoid renal cell carcinoma

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A radical nephrectomy specimen is received. Which area is most likely to contain sarcomatoid component of renal cell carcinoma?


1. The area designated by letter "A".
2. The area designated by letter "B".
3. The area designated by letter "C".

C. Though there are multiple areas suspicious for sarcomatoid renal cell carcinoma, part C is most suspicious as this shows a more whitish, fleshy cut surface that appears to be different from the surrounding tumor. The yellow background of the tumor is consistent grossly with a clear cell renal cell carcinoma.

Reference: Kidney tumor - Sarcomatoid renal cell carcinoma

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