What key factor differentiates ductal carcinoma in situ (DCIS) subtypes?

The differentiation of ductal carcinoma in situ (DCIS) subtypes is primarily based on their histological characteristics. Histology involves studying the microscopic structure of cells and tissues, which provides essential information about the tumor's behavior, growth patterns, and potential for progression. In the case of DCIS, the subtypes can vary by features such as cellular atypia, necrosis, and the arrangement of ductal cells.

For instance, some subtypes of DCIS exhibit higher nuclear grade and comedonecrosis, indicating a more aggressive nature, while others might show lower-grade features associated with a better prognosis. This histological classification is crucial because it significantly impacts clinical management decisions, including the necessity for surgical intervention or adjuvant therapy.

The size of the tumor, patient's age, and location of tumors may have clinical significance in breast cancer management, but they do not fundamentally classify DCIS subtypes in the way that histological characteristics do.