The side and size of breast tumours.

A small series of breast carcinomas in which more node-negative cases presented in the left breast and more node-positive in the right has been extended to include 161 cases, 96% of all presenting in the district over a 12 month period. The previous finding was confirmed. The idea that this might be due to women finding it easier to palpate a small tumour in the left breast is substantiated, as smaller benign lesions presented in the same population on the left, except in the summer months, when the smallest benign lesions were found on both sides. It does not, however, seem possible to explain, on a behavioural basis, the further finding that few cancers under 2 cm in diameter presented in the second part of the year. This raises the possibility that a biological mechanism may be responsible, especially as there was no dearth of small benign lesions at this time.