Cancer of the breast. Gross and histologic pathlogy.

Increased demands are made upon the pathologist to work closely with the surgeon and the mammographer in the interest of early detection. The smallest of cancers and the very earliest phases of neoplastic development are being detected, necessitating fine discriminations between cancer and noncancer. Agreement is not always uniform at these new frontiers of diagnosis, and accuracy is paramount. Tumors are populations of heterogeneous cells. Their morphology lends itself poorly to simple categorization, and their biology is not always accurately reflected in their gross and histologic appearances. Clearly evident to the pathologist are the limitations of morphology, of the light microscope and of routine techniques for examining surgical specimens. Paradoxically, "noninvasive" cancers occasionally metastasize, and lymph nodes originally "free" of cancer are found to contain metastases on more meticulous re-examination. Notwithstanding these limitations a prognostic statement can be made with relative confidence with regard to certain morphologic types of carcinoma. Pure intraductal carcinoma and lobular carcinoma in situ entail negligible threat to normal life expectancy if the breast is thoroughly removed. Other types with a favorable prognosis are intracystic papillary carcinomas and pure mucinous carcinomas. Tumors classified as well differentiated or tubular adenocarcinoma infrequently metastasize and have excellent prospects for cure. Unfortunately, these and other favorable histologic types comprise less than one quarter of all mammary carcinomas. Most carcinomas are without such distinctive features. In this category the degree of anaplasia and the nature of the tumor borders, as well as the presence or absence of blood vessel invasion, dermal lymphatic invasion and metastases in regional lymph nodes, are of major importance in arriving at an estimate of prognosis.