Breast cancer is a type of cancer that develops in the cells of the breasts. It is one of the most common cancers affecting women worldwide, though it can also occur in men. The exact cause of breast cancer is not known, but it is believed to occur when breast cells grow abnormally and multiply faster than healthy cells. Over time, these cells can form a mass or lump called a tumor. There are several types of breast cancer, including: Ductal carcinoma in situ (DCIS): This is the earliest stage of breast cancer that begins in the cells of the ducts. Invasive ductal carcinoma (IDC): This is the most common type of breast cancer. It starts in a milk duct, breaks through the wall of the duct, and invades the fatty tissue of the breast. Invasive lobular carcinoma (ILC): This type of cancer begins in the lobules (milk-producing glands) and can spread to other parts of the body. Inflammatory breast cancer (IBC): This is a rare but aggressive type of breast cancer that makes the breast appear red and swollen. The symptoms of breast cancer can include changes in the size or shape of the breast, changes to the skin over the breast, changes in the appearance of the nipple, and a lump or thickening in the breast or underarm area. It's important to get regular screenings, such as mammograms, to detect breast cancer early when it's most treatable.