[Prevalence of tumors in the left breast]

The present investigation was undertaken to study the laterality of breast tumors on the basis of the Estonian Cancer Registry data for the period of 1968-1981 and special breast screening data for 1974-1983. The ratio of the patients with the left- and right-sided disease was 1.12 (p less than 0.001) for breast cancer, 1.75 (p less than 0.001)--for fibroadenomatosis of the mammary gland, and 1.43 (p less than 0.001)--for mastodynia. Left-sided carcinoma was more common in patients with left nipple discharge which was accompanied by "early menarche" more often than discharge from the right nipple (p less than 0.05). There was no significant difference in the patients' survival versus the laterality of breast cancer.