Four types of invasive ductal carcinoma are less common:
Medullary ductal carcinoma: This type of cancer is rare and accounts for only 3 percent to 5 percent of breast cancers. It is called “medullary” because, under a microscope, it resembles part of the brain called the medulla. Medullary carcinoma may occur at any age, but it typically affects women in their late forties and early fifties. Medullary carcinoma is more common in women who have a BRCA1 gene mutation. Medullary tumors are often “triple-negative,” which means they evaluate negative for estrogen and progesterone receptors and the HER2 protein. Medullary tumors are less likely to involve the lymph nodes, are more responsive to treatment, and may have a better prognosis than more common types of invasive ductal cancer.
Surgery is typically the first-line treatment for medullary ductal carcinoma. A lumpectomy or mastectomy may be performed, depending on the location of the tumor. Chemotherapy and radiation therapy may also be used.
Mucinous ductal carcinoma: This type of breast cancer accounts for less than 2 percent of breast cancers. Microscopic evaluations reveal that these cancer cells are surrounded by mucus. Like other types of invasive ductal cancer, mucinous ductal carcinoma begins in the milk duct of the breast before spreading to the tissues around the duct. Sometimes called colloid carcinoma, this cancer tends to affect women after they have gone through menopause. Mucinous cells are typically positive for estrogen and/or progesterone receptors and negative for the HER2 receptor.
Surgery is typically recommended to treat mucinous ductal carcinoma. A lumpectomy or mastectomy may be performed, depending on the size and location of the tumor. Adjuvant therapy, such as radiation therapy, hormonal therapy, and chemotherapy, may also be required. Most mucinous carcinomas evaluate negative for receptors for the protein HER2, so they are not typically treated with trastuzumab (Herceptin®).
Papillary ductal carcinoma: This cancer is rare, accounting for less than 1 percent of invasive breast cancers. In most cases, these types of tumors are diagnosed in older, postmenopausal women. Under a microscope, these cells resemble tiny fingers or papules. Papillary breast cancers are typically small and test positive for the estrogen and/or progesterone receptors and negative for the HER2 receptor. Most papillary carcinomas are invasive and are treated like invasive ductal carcinoma.
Surgery is typically the first-line treatment for papillary breast cancer. A lumpectomy or mastectomy may be performed, depending on the size and location of the tumor. After surgery, adjuvant therapy may be required and may include radiation, chemotherapy, and/or hormone therapy.
Tubular ductal carcinoma: Another rare type of IDC, this cancer makes up less than 2 percent of breast cancer diagnoses. Like other types of invasive ductal cancer, tubular breast cancer originates in the milk duct and then spreads to tissues around the duct. Tubular ductal carcinoma cells form tube-shaped structures. Tubular ductal carcinoma is more common in women older than fifty. Tubular breast cancers typically evaluate positive for the estrogen and/or progesterone receptors and negative for the HER2 receptor.
Treatment options for tubular ductal carcinoma depend on the aggressiveness of the cancer and its stage. Treatment often consists of surgery, which includes a lumpectomy or mastectomy, and additional (adjuvant) therapy, which may include chemotherapy, radiation, and/or hormone therapy.
Invasive ductal carcinoma, also known as infiltrating ductal carcinoma or IDC, is the most generic form of breast cancer, accounting for 80% of all breast cancer diagnoses.
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