Ultrastructural observations on the basal lamina in the normal human breast.

The ultrastructure of the basal lamina of histologically normal human breast tissue was determined in 19 women undergoing operations for removal of a fibroadenoma or reduction mammoplasty. The day of the menstrual cycle was determined by hormone assay and direct questioning. Previously documented ultrastructural appearances were confirmed: in addition, three morphological variants were found. In all tissue examined, there was reduplication of basal lamina in some areas, which has been described previously as a pathological feature. Also, there was complex branching of the basal lamina into the periductular connective tissue. Some projections contained cytoplasmic processes and, in almost all, hemidesmosomes were seen. The third variant consisted of loops of basal lamina thrown up in folds into the collagenous stromal cuff. Reduplication of basal lamina was detected in breast tissue removed at all stages of the menstrual cycle, looping was not and could not be related to any particular phase of the menstrual cycle. However, complex branching was seen predominantly in the periovulatory and early luteal phase. We conclude that these appearances are normal variants of basal lamina. The appearance of branching basal lamina in the luteal phase suggests that this may be produced in response to endocrine stimulation.