Breast duct micro-endoscopy: a study of technique and a morphological classification of endo-luminal lesions

Endoscopic visualisation of the human mammary ductal system has been sporadically reported over the last decade. Recent rapid and groundbreaking developments in the field of optics have made the previously unseen labyrinth of mammary ducts more easily accessible to direct visualisation and examination. The emphasis so far has been on visualisation of ectatic ducts with pathological nipple discharge. The purpose of this study was to assess the feasibility of mammary duct epithelium in patients with a range of other pathologies. Based on our findings we have developed a morphological classification of endo-luminal lesions seen on endoscopy. We successfully conducted ex vivo mammary duct micro-endoscopy on 115 ducts in 35 mastectomy specimens. Visualisation of mammary duct epithelium was achieved using a solid rod depth of field imaging micro-minimally invasive (DOFI MMI, Acueity Inc., USA) and more recently the LaDuScope (PolyDiagnost GmbH, Germany) system. Both these systems consist of 0.9 mm maximum outer diameter micro-endoscope, with working channels 0.35 and 0.45 mm, respectively. Saline or air insufflation was used to keep the mammary ducts from collapsing. An average of 3.3 (median 3) mammary ducts could be identified and cannulated in all 35 mastectomy specimens (total of 115 ducts). Visualisation beyond 2 cm of the ductal system was possible in 23/35 (66%) of specimens. Abnormalities were visualised in 40% of the ducts. The maximum depth we could negotiate to was 8.9 cm and in doing so manoeuvred past eight duct divisions. In 34% of ducts cannulated, we were able to navigate the scope beyond at least one bifurcation of the principal duct and in 16% of cases extensive intra-ductal navigation was possible. Peripheral ducts were visualised in 16% of cases. False passages were created in 16% of cases. Previous history of smoking, parity, breastfeeding and radiotherapy offered neither significant advantages nor disadvantages for the technique nor did they increase or decrease the number of normal ducts visualised per specimen. This study showed that mammary duct micro-endoscopy is a practical and technically feasible procedure even in the absence of nipple discharge, in normal non-ectatic milk ducts. A simple morphological classification of endoscopically visualised intra-ductal abnormalities is suggested.