Name the most common type of breast cancer that leads to mastectomy.

Invasive ductal carcinoma is indeed the most common type of breast cancer that leads to mastectomy. This cancer originates in the milk ducts of the breast and, as it becomes invasive, it has the potential to spread to surrounding breast tissues and beyond. Due to its prevalent nature and the likelihood of being diagnosed in more advanced stages, many women diagnosed with invasive ductal carcinoma may opt for a mastectomy as a treatment option to remove the tumor and reduce the risk of recurrence.

Invasive lobular carcinoma, while also a form of invasive breast cancer, is less common than invasive ductal carcinoma. DCIS, or Ductal Carcinoma In Situ, is considered a non-invasive cancer where the cells are confined to the ducts, and it may not require a mastectomy, often being treated with lumpectomy or other strategies. Paget's disease of the nipple, though it can be associated with breast malignancy, represents a rare form of breast cancer affecting the skin of the nipple itself. The overall understanding of these conditions highlights the prominence of invasive ductal carcinoma in breast cancer cases leading to mastectomy.