Breast cancer can be divided into different types based on the microscopic characteristics of the tumor cells. Breast cancer is usually adenocarcinoma, which means that the cancer cells originate from glandular tissue. There are also other types, such as sarcomas that originate from muscle, fat, or connective tissue. In some cases, it can also be a combination of different types or carcinoma in situ and invasive carcinoma. Ductal carcinoma in situ Ductal carcinoma in situ is non-invasive breast cancer, a precancerous lesion that has the potential to progress to invasive cancer, but there is no way to predict this. DCIS means that the cells arranged in the ducts have become cancerous. The difference between ductal carcinoma in situ and invasive carcinoma is that the cells do not spread through the duct wall into the surrounding breast tissue. Invasive ductal carcinoma Invasive ductal carcinoma is the most common type of breast cancer that originates in the ducts and breaks through the duct wall and then infiltrates into the adipose tissue of the breast. As a result, IDC can spread to other parts of the body through the lymphatic system or bloodstream. About 8 out of 10 cases of invasive breast cancer are IDC. Invasive lobular carcinoma Invasive lobular carcinoma originates in the lobules of the breast and, similar to IDC, ILC can spread to other parts of the body. About 1 in 10 cases of invasive breast cancer is ILC, which is more difficult to detect by mammography than IDC. Inflammatory breast cancer, a rare invasive breast cancer, accounts for 1 to 3 percent of all breast cancers and has a high metastatic rate and poor prognosis. There is usually no visible lump. Inflammatory breast cancer causes redness and warmth of the breast skin, thickening of the breast skin and an orange peel-like appearance caused by cancer cells blocking lymphatic vessels. The diseased breast may become large, hard, tender or itchy. In the early stages, IBC is often misdiagnosed as a breast infection; however, in the case of IBC, antibiotic treatment will not be effective, at which point a biopsy will reveal cancer cells. Because there is no actual lump, IBC cannot be detected by mammography screening for early lesions. Breast Paget’s disease This type of breast cancer is very rare, accounting for about 1% of breast cancers, and originates in the ducts and spreads to the skin of the nipple and then to the areola. The nipple and areola often appear crusty, scaly, and red, bleeding or oozing, and may feel burning or itchy. Paget’s disease will usually be associated with DCIS or IDC and often requires a mastectomy. If there is no lump in the breast tissue and the biopsy shows DCIS and no invasive cancer, the prognosis is usually good. If it shows invasive, the prognosis is poor and requires staging and treatment like other invasive carcinomas. Angiosarcoma of the breast Angiosarcoma arises from blood vessels or lymphatic vessels, rarely occurs in breast tissue, and is usually a rare complication of radiation therapy. Angiosarcomas can proliferate and spread rapidly, and treatment is consistent with other sarcomas. Special types of invasive breast cancer 1. Better prognosis than invasive ductal carcinoma Adenoid cystic carcinoma, low-grade adenosquamous carcinoma, medullary carcinoma, mucinous carcinoma, papillary carcinoma, ductal carcinoma 2. Prognosis similar to or worse than invasive ductal carcinoma Carcinoma of anaplasia, micropapillary carcinoma, mixed carcinoma