Kidney: Practice Question
What is the most likely diagnosis of this 3.2 cm renal mass that was positive for PAX2 and c-kit / CD117, focally positive for vimentin, and negative for CK7 and CD10?
- Oncocytoma
- Chromophobe carcinoma
- Clear cell renal cell carcinoma
- Papillary renal cell carcinoma
Show Answer and Explanations
Oncocytoma — Correct answer
Correct. Oncocytoma has smooth regular nuclear membranes and abundant granular cytoplasm. It is negative for CK7, while chromophobe carcinoma is positive for CK7. Oncocytoma can show some focal vimentin positivity, particularly near the central scar. In addition, Hale's colloidal iron is patchy at most in oncocytoma, and it is diffusely positive in chromophobe carcinoma.Chromophobe carcinoma
Incorrect. Chromophobe carcinoma has more variation in cell size, bare nuclei, and more irregular nuclear membranes. It is positive for CK7 and diffusely positive for Hale's colloidal iron.Clear cell renal cell carcinoma
Incorrect. Clear cell RCC has a relatively low N/C ratio due to abundant cytoplasm. The cytoplasm can be vacuolated, wispy or granular. Progressing from low grade to high grade tumors, the nuclei will have more irregular borders, larger and more prominent nucleoli, and the cells become more discohesive. CD10 is highly sensitive but not very specific. PAX2 is sensitive but not as specific as PAX8. PAX8 is sensitive and more specific (it also stains mullerian serous carcinoma and thyroid carcinoma). Clear cell RCC is positive for CAIX and vimentin.Papillary renal cell carcinoma
Incorrect. Papillary RCC is positive for CD10, CK7, vimentin and AMACR.Summary
Summary:| Marker | Clear cell carcinoma | Papillary | Oncocytoma | Chromophobe |
|---|---|---|---|---|
| CD10 | + | + | - | -/+ |
| PAX2 | + | + | + | - |
| Vimentin | + | + | - | - |
| CK7 | - | + | - | + |
| CAIX | + | - | - | - |
| c-kit | - | - | + | + |
| AMACR | - | + | - | - |