Sarcomatoid Renal Cell Carcinoma

Definition

Renal cell carcinoma of any type exhibiting at least focal sarcomatoid/spindle cell differentiation

Represents a form of high grade transformation, not a distinct subtype of renal cell carcinoma
- May occur in any of the standard subtypes of renal cell carcinoma
- Reported to occur in 5-8% of renal cell carcinomas
  - Less common in our experience
- Should not be reported as the subtype of renal cell carcinoma
Requires evidence of epithelial differentiation
- Concurrent areas of renal cell carcinoma of any type, OR
- Immunohistochemical positivity for keratin or EMA
  - (Keratin and EMA expression may be appropriate for some sarcomas, including leiomyosarcomas)
Requires a spindle cell component measuring at least one low power (40x) field
- May be discrete or intermixed with epithelial elements
- May be very focal
Most common patterns are fibrosarcoma and malignant fibrous histiocytoma
- Rare cases reported with patterns of rhabdomyosarcoma, chondrosarcoma, osteosarcoma and hemangiopericytoma
- Pattern does not appear to affect prognosis
Grade of sarcoma is not clinically significant
- May range from low to high
  - Based on cellularity, atypia, mitotic figures
See Classification/Lists in menu at left for links to specific carcinoma subtypes

John P Higgins MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting:: January 24, 2011