Hamartomas of the breast are well circumscribed tumour-like lesions composed of fibroadipose and glandular tissue in variable degrees, depending on the patients' age. The nodules have a pseudocapsule and can easily be enucleated surgically. They may be recognised on mammography by their contours and density. Clinically they appear as painless areas of induration most frequently in the fourth and fifth decade of life. Pathogenetically it is assumed that they are an additional sprout of the breast, comparable to an "intra-glandular polymastia".