This study by H. J. G. Bloom and W. W. Richardson examines the histological grading of breast cancer and its impact on prognosis in a series of 1409 cases, with 359 patients followed for 15 years. The authors highlight the limitations of clinical staging in assessing the prognosis of breast cancer due to the wide variation in tumor behavior even among patients with similar clinical presentations. They introduce a histological grading system based on three factors: degree of structural differentiation, variation in nuclear characteristics, and frequency of hyperchromatic and mitotic figures. The tumors are classified into three grades (low, intermediate, and high) to predict survival rates over 5, 10, and 15 years. The results show a significant correlation between histological grade and survival, with patients having low-grade tumors having a much higher survival rate compared to those with high-grade tumors. The study also discusses the challenges in grading, such as histological preparation quality, variation in tumor appearance, and the impact of metastases. The authors conclude that histological grading is a valuable tool for predicting prognosis and guiding treatment decisions, particularly in assessing the likelihood and speed of metastasis development.This study by H. J. G. Bloom and W. W. Richardson examines the histological grading of breast cancer and its impact on prognosis in a series of 1409 cases, with 359 patients followed for 15 years. The authors highlight the limitations of clinical staging in assessing the prognosis of breast cancer due to the wide variation in tumor behavior even among patients with similar clinical presentations. They introduce a histological grading system based on three factors: degree of structural differentiation, variation in nuclear characteristics, and frequency of hyperchromatic and mitotic figures. The tumors are classified into three grades (low, intermediate, and high) to predict survival rates over 5, 10, and 15 years. The results show a significant correlation between histological grade and survival, with patients having low-grade tumors having a much higher survival rate compared to those with high-grade tumors. The study also discusses the challenges in grading, such as histological preparation quality, variation in tumor appearance, and the impact of metastases. The authors conclude that histological grading is a valuable tool for predicting prognosis and guiding treatment decisions, particularly in assessing the likelihood and speed of metastasis development.