Aspects of the normal human breast
Studies have been made on normal tissue from 50 whole breasts and 43 breast biopsies using subgross histological and duct injection techniques. The results obtained from the various investigations have been compared with factors which may affect the breast, notably age, the menstrual cycle, parity and laterality. It has been found that the ducts in the breast do not branch in a simple dichotomous manner, nor are individual lactiferous systems arranged about the nipple in discrete lobes like the spokes of a wheel. Rather, the duct systems are interwoven with each other in an intricate manner and may not be dissected out individually. The quantity of parenchymatous lobules in the breast was found to decrease significantly with age. Lobules occurred in areas of high focal density and their number was not related to the amount of fibrous stroma present. Lobules did not occur with greater frequency in the upper outer quadrant of the breast and lobule number was not related to tumour incidence. Parity and laterality were without significance in the present study. The presence of acid mucopolysaccharides in the intra-lobular breast stroma showed a cyclical variation which peaked at approx¬ imately day 24 of the menstrual cycle. It is suggested that hyaluronic acid is the principal component of the staining reaction and may be associated with premenstrual water retention in the breast. The incidence of intraluminal secretions within the ductules of lobules, and intracellular granules within ductular cells, did not reveal cyclical variation. Normal lobule types occurring in whole breasts were assessed by subgross techniques and significant variations were recorded with age. Parity and laterality were not of significance in these results. Examination of breasts following injection of lactiferous ducts with a radio-opaque medium indicated that more than one subgross lobule type was associated with a single lactiferous duct system. Comparisons have been made between the radiographic and subgross morphology of slices of breast tissue and results suggest that the parenchymal content of the breast cannot be predicted from radiographic appearances alone.