An original stereomicroscopic analysis of the mammary glandular tree.

In the 1970s, Wellings developed and reported extensively on a technique for a three-dimensional (3D) analysis of breast lesions. Drawbacks of this subgross sampling technique were that it was laborious, rather time-consuming and only allowed prospective studies. Furthermore, the stereomicroscopic aspect of the lesions studied was not diagnostic and each sample had to be studied histologically after paraffin embedding to determine the diagnosis. The present study introduces an original method enabling the exploration of the 3D structure of the mammary glandular tree from a paraffin-embedded sample. This procedure is quicker than the Wellings' technique, permits retrospective study and enables a 3D analysis of previously identified histological structures. Stereomicroscopic aspects of non-malignant lesions such as single multiple or metaplastic cysts, adenosis, ductal-lobular hyperplasia and malignant in situ neoplasms are illustrated. Our results confirm Wellings' concept that most minimal lesions arise in the terminal ductulo-lobular units. We also show that ductal carcinoma in situ may grow continuously by extending through the glandular tree but may also have a multifocal or stepwise progression in some cases.