What is the tumor grading system in oncology (oncology)?

From the Guidelines

The most widely accepted grading system in oncology is the Gleason score, which grades prostate cancer tumors from 2 to 10 based on the two most predominant glandular patterns. This system is crucial for determining prognosis and treatment planning, as higher-grade cancers typically require more aggressive treatment approaches 1. The Gleason score combines two grades from 1 to 5, with lower scores indicating well-differentiated tumors and higher scores indicating poorly differentiated tumors. For example, a Gleason score of 2 (1 + 1 = 2) indicates the most highly differentiated type of tumor and thus the best prognosis, while a score of 10 (5 + 5 = 10) indicates the most poorly differentiated tumor, with the worst prognosis.

Some key points to consider when using the Gleason score include:

• Gleason grade 4 (and higher) tumors carry a significantly worse prognosis than do Gleason grade 3 (and lower) tumors 1
• The order of the grades matters, with Gleason 4 + 3 = 7 tumors carrying a worse prognosis than Gleason 3 + 4 = 7 1
• The TNM staging system, which describes the tumor size (T), lymph node involvement (N), and metastasis (M), complements the Gleason score in determining prognosis and treatment planning 1

It's worth noting that while the Gleason score is specific to prostate cancer, other cancer types may use different grading systems, such as the Nottingham grading system for breast cancer. However, the principle of grading cancer cells based on their abnormality and growth potential remains a fundamental aspect of oncology. Pathologists determine the grade by examining tissue samples obtained through biopsies or surgical resections, looking at cellular characteristics such as differentiation, mitotic activity, and nuclear features.

From the Research

Grading System in Oncology

The grading system in oncology is used to predict the clinical behavior of malignancies, establish appropriate therapies, and facilitate exchange of precise information between clinicians.

• The internationally accepted criterion for cancer staging is the tumor-node-metastasis (TNM) system, which includes:
  • Tumor size and local growth (T)
  • Extent of lymph node metastases (N)
  • Occurrence of distant metastases (M) 2, 3
• The TNM classification system has evolved over the years to accommodate increasing knowledge about cancer biology, with efforts to keep the system synchronized with the most sophisticated cancer technology and simple for ease of clinician/patient use 2, 3

Updates to the TNM Staging System

There have been updates to the TNM staging system, including:

• The seventh edition of the TNM classification, which is based on the proposals of the Staging Project of the International Association for the Study of Lung Cancer (IASLC) 4
• The eighth edition of the TNM classification, which updates cancer staging according to the evidence accumulated in the last 8 years since the release of the seventh edition 5, 6
• The inclusion of biomarkers, such as estrogen receptor (ER) and progesterone receptor (PR) expression, HER2 expression, and/or amplification, and histologic grade, in the staging classifications 5

Application of the TNM Staging System

The TNM staging system is applied to various types of cancer, including:

• Breast cancer, where the eighth edition of the AJCC TNM staging system integrates biomarkers with anatomic definitions 5
• Lung cancer, where the seventh edition of the TNM classification is used to validate the TNM descriptors 4
• Colorectal cancer, anal cancer, and appendiceal cancer, where the eighth edition of the TNM classification updates cancer staging according to the evidence accumulated in the last 8 years since the release of the seventh edition 6