## Fuhrman Grading System for Renal Cell Carcinoma **Key Point:** The Fuhrman system is based on **nuclear size, shape, and nucleolar prominence** as viewed under standard light microscopy. | Grade | Nuclear Size | Nucleoli | Nuclear Irregularity | Chromatin | |-------|--------------|----------|----------------------|-----------| | 1 | Small (10 μm) | Inconspicuous/absent | Regular, round | Fine | | 2 | Intermediate (15 μm) | Visible at ×400 only | Slight irregularity | Fine to coarse | | **3** | **Large (20 μm)** | **Visible at ×100** | **Marked irregularity** | **Coarse** | | 4 | Very large (>20 μm) | Prominent | Severe irregularity | Coarse; multinucleate/bizarre | **High-Yield:** The **transition from Grade 2 to Grade 3** is marked by: - Nucleolar visibility shifting from ×400 (high power) to ×100 (low power) - Increased nuclear irregularity and coarseness - This is the most clinically significant prognostic threshold in RCC grading **Clinical Pearl:** Grade 3–4 RCCs have significantly worse prognosis and higher metastatic potential compared to Grade 1–2.
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