The growing female breast is a very radiosensitive organ. In the series of 14 patients, only doses of 100 roentgen or less absorbed in the breast bud during the first year of life have caused no distortion of the development of the breast. Doses of 300 R and more (in the breast) interfered with its proper maturation despite fractionation and radition treatment at 50 kilovolt (peak) kp (contact x-ray therapy). Also the radiations in the vicinity of the areola mammae must be taken into account with respect to scattered radiations absorbed in the epithelial buds of the breast. For this reason, as well as for permanent functional and cosmetic sequelae, radiations around the mammary area should be avoided in young girls during the prepubertal age for all nonmalignant tumors.
Jaromir Kolar, Vaclav Bek, Radko Vrabec. Hypoplasia of the Growing BreastAfter Contact X-ray Therapy for Cutaneous Angiomas. Arch Dermatol. 1967;96(4):427–430. doi:10.1001/archderm.1967.01610040077014