Contributor: Gordon K. Klintworth
Carcinoma of the breast is extremely common and in women it remains the leading cause of death from cancer. Survival rates have improved over the pat three decades as result of better eraly diagnostic techniques and innovative therapy. The strongest risk factor is a positive family history is of breast cancer. Germline mutations in BRCA1 and BRCA2 account for ~80% of inherited breast cancer. Individuals with Louis-Bar syndrome have an increased susceptibility to breast carcinoma even in heterozygous carriers. Almost all carcinomas of the breast are adenocarcinomas derived from the glandular epithelium of the terminal duct lobular unit. Several different types are recognized including invasive ductal adenocarcinoma. There are three types of carcinoma-in-situ (intraductal carcinoma, lobular carcinoma in situ and intraductal papillary carcinoma). Invasive carcinoma is divided into several histological subtypes that vary in frequency: infiltrating ductal carcinoma (~80%), lobular carcinoma (~5%)[carcinoma - lobular], medullary carcinoma  [carcinoma - medullary] (~6%), colloid carcinoma [carcinoma - colloid] (~2.5%), Paget disease (~2.3%), mucoepidermoid carcinoma and other less common types. Colloid carcinoma of the breast is an uncommon type of breast carcinoma that occurs in older women. It has a better prognosis that the infiltrating ductal carcinoma. Medullary carcinoma of the breast is an invasive tumor that lacks calcification. Microscopically it has highly pleomorphic cells and numerous mitotic figures. The periphery of the tumor is infiltrated by lymphocytes. Despite the ominous histopathologic features the prognosis is better than for the more common infiltrating ductal carcinoma and lobular carcinoma of the breast.Carcinomas of the breast can spread by the lymphatic vessels to the regional lymph nodes. Distant metastases can reach distant sites including the uvea and orbit [carcinoma - metastatic]. Some patients with cancer associated retinopathy have been associated with carcinoma of the breast. HER-2 is amplified and overexpressed in 20-30% of invasive breast carcinomas and is linked to a poor clinical outcome. Its amplification predicts a positive response to trastuzumab in chemotherapy. Docetaxel is a commonly used antineoplastic agent. It sometimes causes a maculopathy that resembles niacin maculopathy [maculopathy - niacin].