The Scarff-Bloom-Richardson (SBR) score, often referred to as the Nottingham Histologic Grade (NHG) or Elston-Ellis modification, is a numerical system used to assess the aggressiveness of certain cancers, most notably breast cancer. It provides a grade (typically I, II, or III) based on the microscopic appearance of cancer cells.
The SBR score is derived by evaluating three specific histological features of tumor cells, each assigned a numerical score, which are then summed up to determine the final grade.
Components of the SBR Score
The SBR grading system evaluates three distinct features on histological sections. Each feature is scored from 1 to 3 points, with higher scores indicating more aggressive features.
| Histological Feature | Score 1 (Low Grade) | Score 2 (Intermediate Grade) | Score 3 (High Grade) |
|---|---|---|---|
| **1. Tubule Formation** (Percentage of tumor forming tubules) | >75% tubule formation | 10-75% tubule formation | <10% tubule formation |
| **2. Nuclear Pleomorphism** (Variation in nuclear size and shape) | Small, uniform nuclei | Moderate variation in nuclei | Marked variation, bizarre nuclei |
| **3. Mitotic Count** (Number of mitotic figures per 10 high-power fields, HPF) | Low mitotic activity (e.g., 0-7 mitoses/10 HPF) | Moderate mitotic activity (e.g., 8-15 mitoses/10 HPF) | High mitotic activity (e.g., >15 mitoses/10 HPF) |
Note: The specific cut-offs for mitotic count can vary slightly between laboratories and protocols, but the principle of low, moderate, and high activity remains consistent.
Calculating the SBR Score and Assigning Grade
The individual scores for tubule formation, nuclear pleomorphism, and mitotic count are summed to obtain a total SBR score. This total score then corresponds to a specific SBR grade:
- Total Score Range: The minimum possible score is 3 (1+1+1) and the maximum is 9 (3+3+3).
- Grade Assignment:
- Grade I (Low Grade): Total Score of 3 to 5
- Grade II (Intermediate Grade): Total Score of 6 to 7
- Grade III (High Grade): Total Score of 8 to 9
Purpose and Significance of the SBR Grade
The Scarff-Bloom-Richardson (SBR) grade is a crucial prognostic and predictive factor in oncology, particularly for breast cancer. As a well-established tool, its primary purpose is to guide the selection of adjuvant systemic therapy. This means it helps medical professionals determine the most appropriate post-surgery treatments, such as chemotherapy, hormone therapy, or targeted therapy, to reduce the risk of cancer recurrence.
-
Clinical Implications:
- Grade I tumors are generally less aggressive, have a better prognosis, and may require less intensive adjuvant therapy.
- Grade II tumors represent an intermediate level of aggression.
- Grade III tumors are typically more aggressive, have a higher risk of recurrence and metastasis, and often necessitate more aggressive systemic therapies.
-
Evaluation Flexibility: Grade evaluation is traditionally performed on histological sections (tissue biopsies). However, advancements allow for grade evaluation on cytology smears as well. This capability is significant as it can avoid and minimize the morbidity associated with overtreatment of lower grade tumors, ensuring that patients receive treatment proportionate to the tumor's actual aggressiveness. This can lead to fewer side effects and improved quality of life for patients with less aggressive cancers.
The SBR score provides valuable information about a tumor's biological behavior, aiding clinicians in making informed treatment decisions tailored to individual patient needs.
