Other Types
Though the most common breast cancer type is invasive ductal carcinoma (IDC), there are other types that are less commonly seen. Other types of breast cancer include:
Medullary carcinoma
Medullary carcinoma accounts for 3-5% of all breast cancer types. The tumor usually shows up on a mammogram, but does not always feel like a lump. At times, it feels like a spongy change of breast tissue.
Tubular carcinoma
Making up about 2% of all breast cancer diagnoses, tubular carcinoma cells have a distinctive tubular structure when viewed under a microscope. It is usually found through a mammogram and is a collection of cells that can feel like a spongy area of breast tissue rather than a lump. This type of breast cancer is known for being slow-growing and is usually associated with DCIS. Typically, this type of breast cancer is found in women aged 50 and above and usually responds well to hormone therapy.
Mucinous carcinoma (colloid)
Mucinous carcinoma represents approximately 1-2% of all breast cancers. The main differentiating features are mucus production and cells that are poorly defined. It also has a favorable prognosis in most cases.
Paget’s disease of the breast or nipple
This condition (also known as mammary Paget’s disease) is a rare type of cancer affecting the skin of the nipple and often the areola, which is the darker circle of skin around the nipple. Most people with Paget’s disease evident on the nipple also have one or more tumors inside the same breast; generally, either ductal carcinoma in situ or invasive breast cancer (1–3). Paget’s disease is frequently misdiagnosed at first because the first noticeable symptoms can easily be confused with more common skin conditions affecting the nipple. Like all breast cancers, the prognosis for Paget’s disease depends on a variety of factors, including the presence or absence of invasive cancer and whether or not it has spread to nearby lymph nodes.
Metaplastic breast cancer
Metaplastic breast cancer is a very rare and aggressive form of breast cancer. It accounts for less than 1% of all breast cancer diagnoses. Metaplastic breast cancer often resembles invasive ductal carcinoma (IDC) on imaging scans, making a correct diagnosis difficult.
Phyllodes tumors
Phyllodes tumors in the breast are usually benign (non-cancerous), with only a small percentage found to be malignant (cancerous). Though rare, the presence of malignant phyllodes tumors in the breast often requires a mastectomy as part of treatment. It is necessary to get very wide margins around the tumor in order to prevent it from recurring, or coming back, in the same place.
Angiosarcoma of the breast
Angiosarcoma of the breast is an extremely rare form of breast cancer, accounting for only 0.1% to 0.2% of all breast cancers. It occurs in the breast and in the skin of the arms, and is usually seen in those who have had extensive prior radiation of the chest wall, such as mantle radiation for cancer treatment as a child or young person. Angiosarcoma can grow and spread quickly.
Sources:
National Cancer Institute