Popular Concepts Revisited
Today popular conceptions of breast cancer and its management are becoming outmoded as research exposes their lack of merit. Unfortunately, instead of this leading to the modification of common medical procedures, or to the understanding that these protocols are becoming obsolete, many persevere unchanged. Some of the tenets accepted as gospel need revisiting--not only the mastectomy, but also the classification of ductal carcinoma in situ as cancer, the misconception surrounding "early detection," axillary lymph node dissection, radiation following surgery, and intensive postsurgical follow-up (chest x-ray and bone scans), as well as one of the newer therapies--high-dose chemotherapy with bone marrow or stem-cell transplant.

There is not unanimous agreement about what constitutes breast cancer. Breast anatomy may be helpful in understanding how the disease is defined. Breasts house a series of milk-producing glands that empty into smaller and larger tubes called ductules and ducts. Put simply, breast cancer means uncontrolled growth of cells--tissue that, when removed and analyzed by a pathologist, shows that malignant cells have overrun the anatomical boundary of the duct and extend into the surrounding tissue.

The most common form of breast cancer, referred to as "infiltrating ductal carcinoma," comprises 70% to 80% of invasive tumors that arise within the mammary ducts and invade the surrounding fatty tissue (called the stroma). The other 20% to 30% are subtypes (invasive lobular, medullary, mutinous, tubular, adenocystic, papillary, carcinosarcoma, inflammatory). This scheme of classification is based on locale and behavior. Americans might be differentiated geographically--as New Yorkers, Southerners, and Californians--but there are plenty of variations within each regional type.

Breast cancer is not a single disease, but an umbrella term for a plethora of diseases. It is no more homogeneous than infectious diseases--mumps and malaria have as little in common as herpes and cholera. Similarly, breast cancers differ strikingly from one another. Within each tumor itself there is enormous heterogeneity. Tumors are as diverse biologically as Manhattan is socially. A tumor is not composed of a single type of cell. It is like a vegetable basket that contains bits of lettuce, carrots, beets, broccoli, and zucchini indiscriminately fused together. Each vegetable has a unique shape, texture, growing pattern, and chemical composition. A tumor is a biological entity unto itself--like the city of Manhattan--yet the inhabitants of the city neither look alike nor behave, eat, or recreate uniformly. Some tumor cells metastasize early; some never do; others do so slowly. Some are accelerated by estrogen; others are not. Some encourage blood vessel growth; some do not. These processes are determined by the genetic material within the myriad cells that comprise the tumor. Even though it may be reasonable to say that two women have breast cancer, when the disease in the two women is compared, there might be so many differences that one begins to question whether they truly do have the same disease. Rate of growth and infiltration may take 3 years in one woman and 40 years in another.

Ductal Carcinoma in Situ Classification
Some abnormalities look like cancer under the microscope but do not act like it, and therefore are not truly breast cancer. One of these discrepancies between anatomy and behavior is "ductal carcinoma in situ" (DCIS), which consists of an abnormal proliferation of ductal cells that do not invade the basement membrane of that duct (hence the term "in situ," meaning "confined to the site"). Because DCIS does not extend beyond the borders of the duct, it is noninvasive, and does not therefore constitute a true malignancy. In 1934 Halsted's former resident, Joseph Bloodgood,³² described DCIS as precancerous tissue--a depiction that still applies.