True invasive ductal carcinoma accounts for 80% of all invasive tumors, with the final 20% split evenly between lobular carcinoma and special variants of infiltrating ductal carcinoma (24). Mammographically, invasive ductal cancers are characterized by a stellate density or microcalcifications. Macroscopically, gritty, chalky streaks are present within the tumor that most likely represent a desmoplastic response. Invasion of the surrounding stroma and fat, with a fibrotic, desmoplastic reaction surrounding the invasive carcinoma, generally is present.
Special types of infiltrating ductal carcinoma are uncommon and typically account for nearly 10% of all invasive cancers. Medullary carcinoma, which accounts for 5% to 8% of breast carcinomas, arises from larger ducts within the breast and has a dense lymphocytic infiltrate. The tumor appears to be a slower growing and less-aggressive malignancy than other forms of carcinoma. Even when axillary disease is present, the prognosis with medullary carcinoma is better than that of other variants of invasive ductal carcinoma. Mucinous (colloid) carcinoma accounts for 5% of all breast cancers. Grossly, areas of the tumor may appear mucinous or gelatinous, whereas microscopically they are relatively acellular. Infiltrating comedo carcinoma accounts for less than 1% of all breast malignancies and is an invasive cancer characterized by foci of necrosis that exude a comedonecrosis-like substance when biopsied. Usually, comedocarcinomas are in situ malignancies. Papillary carcinoma is predominantly a noninvasive ductal carcinoma; when invasive components are present, it should be specified as invasive papillary carcinoma. Tubular carcinoma, a well-differentiated breast cancer that accounts for 1% to 2% of all malignant breast neoplasms, rarely metastasizes to axillary lymph nodes and tends to have a better prognosis than infiltrating ductal carcinoma. Adenoid cystic carcinomas are extremely rare breast tumors that histologically are similar to those seen in the salivary glands. They are well-differentiated cancers that are slow to metastasize.
Growth Patterns The growth potential of breast cancer and the patient’s resistance to malignancy vary widely with the individual and the stage of disease. The doubling time of breast cancer ranges from several weeks for rapidly growing tumors to months or years for slowly growing lesions. If the doubling time of a breast tumor were constant and a tumor originated from one cell, a doubling time of 100 days would result in a 1-cm tumor in about 8 years (Fig. 40.1) (25). During the preclinical phase, tumor cells may be circulating throughout the body. Because of the long preclinical tumor growth phase and the tendency of infiltrating lesions to metastasize early, many clinicians view breast cancer as a systemic disease at the time of diagnosis. Although cancer cells may be released from the tumor before diagnosis, variations in the tumor’s ability to grow in other organs and the host’s response to tumor cells may inhibit dissemination of the disease. Many women with breast cancer can be treated successfully with surgery alone, and some patients have been cured even in the presence of palpable axillary disease. A pessimistic attitude that breast cancer is systemic and incurable at diagnosis is unwarranted.
13121110987654321 1 mm 1 cm 1 kg 40302010 Number of cell doublings Diameter (cm) 0.5 1 2 8 Premammographic Preclinical Years of growth
Figure 40.1 Growth rate of breast cancer indicating long preclinical phase. (From Gullino PM. Natural history of breast cancer: progression from hyperplasia to neoplasia as predicted by angiogenesis. Cancer 1977;39:2699.)