Although most types of breast cancer are localized in a lobule or duct of the breast, not all of them do. In fact, there are a number of types that are much less common in men and women than ductal or lobular carcinoma. These include but are not limited to: adenoid cystic carcinoma, inflammatory breast cancer (discussed in an earlier post), medullary carcinoma, metaplastic carcinoma, micropapillary carcinoma, mucinous carcinoma, and paget's disease of the breast.
Adenoid Cystic Carcinoma (ACC)
ACC is a relative rare form of cancer which has a tendency to develop in specific sites of the body, e.g. salivary glands, or less commonly in the skin, breast, prostate gland in men, and some other areas. It may be confused with intraductal carcinoma and invasive ductal carcinoma with a sieve-like pattern. ACC is recognised mainly by small basaloid cells (a basaloid cell is a cell usually of the epidermis resembling a basal cell) either with solid, cribriform (perforated like a sieve) or tubular growth patterns which may be mixed but any one may occur more regularly than another. ACC tumors are slow-growing and tend to become progressively worse but are are more likely to be detected than other forms of breast cancer. Fortunately, this type of breast cancer does not usually affect the lymph nodes and is unlikely to spread. There have been reported cases of ACC of the breast ranging from the ages of 19 through 90, in both males and females.Click here to see images of adenoid cystic carcinoma of the breast.
Medullary breast cancer is a special type of invasive breast cancer which has a distinct boundary between normal tissue and tumor (also spelt tumour) tissue. It is also defined by the presence of white cells, also known as immune system cells, which surround the borders of its significantly large cancer cells. This variant of breast cancer has an incidence of 5 in 100 breast cancers and is likely to spread to other areas of the body. Like ACC, medullary carcinoma of the breast may be difficult to distinguish from invasive ductal carcinoma and is treated similarly.
Metaplastic carcinoma is a very rare variant of invasive ductal carcinoma where its cancer cells may be of two or more cell types. Some types of cells present are not indicative of other breast cancer types. These cancer cells tend to remain localized. Metaplastic carcinoma of the breast is also treated similarly to invasive ductal carcinoma but tends not to be sensitive to hormone therapy.
Micropapillary carcinoma is a rare variant of invasive ductal carcinoma which is characterised by small, tightly cohesive tumor cell clusters within clear spaces resembling lymphatic vessels. This type of breast carcinoma is aggressive and favours to spread to the lymphatic system in most cases. Micropapillary growth is normally associated with invasive ductal carcinoma and is rarely seen separately.
Mucinous (Colloid) Carcinoma
Mucinous carcinoma is another rare type of invasive breast cancer which involves mucus-producing cancer cells which grow into a jelly-like tumor. This variant grows quite slow and is very unlikely to spread to the lymph nodes. It has an incidence of about 2 in 100 breast cancers and once treated, further treatment may not be required.
Paget's Disease of the Breast
This begins in the milk ducts of the breast as either an in situ or invasive cancer and spreads to the skin of the nipple before affecting the areola (dark circle around nipple). It appears similar to eczema. The skin of the nipple and areola may look crusted, scaly and red and there may be possible bleeding. The area may also become sore or itchy or may burn. Paget's disease affects 1 or 2 out of 100 women with breast cancer and is usually diagnosed in women aged 50-59.