The development of microendoscopes for visualization of mammary ductal anatomy has progressed rapidly over the past 2 decades. The first published reports of mammary ductoscopy appeared in 1991 authored by Okazaki et al as well as Makita et al in which the endoscopy was performed with essentially a bare fiberoptic cord with no working channel for insufflation or aspiration.1,2 Subsequently, Susan Love published a small series of breast endoscopy in 9 patients with a diagnosis of ductal carcinoma in situ at the time of mastectomy.3 Again, using an early generation instrument, they encountered difficulties with insufflation of the ducts and navigation of ductal branches due to rigidity of the scope. As technology improved, a number of semiflexible microendoscopes emerged, which allowed insufflation via a working channel that was formed by a sheath that surrounded the fiberoptic core. Reports of the feasibility of visualization and navigation to the level of the terminal ductal lobular units were generated initially in human mastectomy specimens and subsequently in patients under local anesthesia.4,5 These technologic developments resulted in visualization of submillimeter intraductal lesions and access into the terminal human mammary ducts, which has spawned a new era of intraductal approaches to diagnosis and treatment of breast diseases.
The anatomy and pathophysiology of the human mammary ductal system is still an area of active research investigation. Murine transgenic models continue to provide insight into the checkpoints and proliferative mechanisms that are critical to development of the mature mammary ductal system. Interestingly, injection molds of human mastectomy specimens date back to the early anatomists such as Sir Astley Paston Cooper, who published his illustrations in the treatise On the Anatomy of the Breast in 1840. A modern counterpart to these anatomic studies has been published by JJ Going which elegantly details the fine arborization of ductal systems that are overlapping but not communicating (Fig. 58-1).6 This pattern of complex arborization has been confirmed in patients undergoing galactography as well. In total, these studies illustrate the anatomic challenges that face investigators who have plans to survey and sample the human mammary ductal system.
Reconstruction of human mammary ductal system. A human mastectomy specimen was injected with artificial materials of different colors to form a cast of the human mammary ductal system. Each color represents a different ductal system. Note the tremendous branching and the overlap of ductal systems which do not communicate. [Reproduced, with permission, from Going JJ, Moffat DF. Escaping from flatland: clinical and biological aspects of human mammary duct anatomy in three dimensions. J Pathol. 2004;203(1):538-544.]
Pathologic nipple discharge (PND) has been subjected to a wide variety of definitions that illustrate one source of variation in comparing patients enrolled in clinical trials at different institutions. One critical defining feature is to differentiate pathologic nipple discharge from physiologic nipple ...