The histologic grade of breast cancer provides information about the appearance of the cancer cells under a microscope. It helps to classify the tumor based on how closely the cancer cells resemble normal breast tissue. The histologic grade is an important factor in determining the aggressiveness of the cancer and can influence treatment decisions. The commonly used histologic grading system for breast cancer is the Nottingham Grading System, also known as the Elston-Ellis modification of the Scarff-Bloom-Richardson grading system. It consists of three grades:
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Grade 1 (Low Grade):
- The cancer cells in Grade 1 tumors closely resemble normal breast cells.
- The cells are well-differentiated, meaning they maintain some of their normal characteristics.
- Grade 1 tumors tend to grow and spread more slowly than higher-grade tumors.
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Grade 2 (Intermediate Grade):
- Grade 2 tumors have cells that are moderately differentiated. They are somewhat different from normal breast cells.
- The characteristics of the cancer cells fall between those of Grade 1 and Grade 3 tumors.
- Grade 2 tumors may have a moderate rate of growth.
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Grade 3 (High Grade):
- Grade 3 tumors have poorly differentiated cancer cells that look very different from normal breast cells.
- The cells are highly abnormal in appearance, and the tumor tends to grow and spread more aggressively.
- Grade 3 tumors are associated with a higher risk of recurrence and a poorer prognosis.
Pathologists determine the histologic grade by examining a tissue sample (biopsy or surgical specimen) under a microscope. They assess various features of the cancer cells, including cell size, shape, and how closely they resemble normal breast cells. The overall grade is then assigned based on the cumulative assessment of these features.
The histologic grade, along with other factors such as tumor size, lymph node involvement, and molecular characteristics (like hormone receptor and HER2 status), is used to determine the stage of breast cancer and guide treatment decisions. Higher-grade tumors may require more aggressive treatment approaches, such as chemotherapy, to reduce the risk of recurrence.
