HISTOLOGIC SPECIFICITY OF EFFECT OF AGE AT BIRTH OF 1ST CHILD ON BREAST-CANCER RISK

Slides of 531 breast cancers from Glamorgan, Wales, were classified according to the presence or absence of each of 3 histologic characteristics: stromal infiltration by linear strands of tumor cells, areas of intraductal carcinoma and areas of lobular carcinoma in situ. The proportion of tumors with each of these characteristics was positively associated with age at 1st child-birth. Increasing age at 1st birth had a strong positive effect on the incidence risk of tumors with any of these features, but only a small effect on risk of tumors with none. For parous women, the rate of breast cancer with or without linear strands, with or without areas of intraductal cancer and without areas of lobular carcinoma in situ was lower than for nulliparous women. Parity appeared not to reduce the risk of tumors with areas of lobular carcinoma in situ.