Stepwise Mammary Carcinogenesis: Immunological Considerations

Abstract

The literature provides ample evidence that mammary carcinogenesis is a nonrandom event influenced by such risk factors as ethnic group, family history, age, parity and, perhaps, nutritional factors (Lilienfeld 1963; Macklin 1959; Vakil and Morgan 1973). It is, therefore, not surprising that patients who develop a cancer in one breast are at a greatly increased risk of developing a second primary breast cancer (Harrington 1946; McCredie et al. 1975). In response to such observations some have gone so far as to recommend prophylactic removal of the “second” breast (Leis 1979). Certainly it is clinically and conceptually important to take note of the increased risk of second breast cancers. However, it may be of even greater importance to consider the paradox that among patients who have the necessary and sufficient requirements to develop breast cancer, only a small minority will develop a primary cancer in the second breast. This is all the more surprising in view of the similarity in microscopic structure, mammographic patterns, and physical proximity of the two breasts. Moreover, the relatively low incidence of second primaries persists regardless of the age at diagnosis of the first lesion, family history, parity, or any constellation of known risk factors.