FDS has made it relatively easy to confirm the diagnosis of pathologic nipple discharge, but there are some clinical problems: which patients require surgery? How to accurately locate and resect the lesion in patients requiring surgery, and how to accurately sample and diagnose the lesion after resection? In view of the above problems, most experts preferred to decide upon the operation after FDS examination has revealed obvious intraductal space-occupying lesions; some experts decided upon the operation by classifying intraductal elevated lesions[4, 5]. The majority of these lesions were concentrated in the main duct as well as in grade 1 to 3 ducts, and these space-occupying lesions were easily detected by FDS. However, most malignant breast tumor originated from small- and medium-sized ducts and terminal ductal lobular units, which were beyond the scope of FDS. Therefore, the diagnosis was easily missed by FDS alone. At the same time, even if FDS detected space-occupying lesions without accurate localization, the extent of intraoperative resection and sampling in the pathology department were difficult; this could cause missed diagnosis.
After localization by methylene blue staining after FDS examination, not only could the lesion be accurately located, but also the pathologists could accurately perform sampling according to the staining of mammary ducts at all levels, so that some patients who were not detected by FDS but actually had space-occupying lesions in the small- and medium-sized mammary ducts underwent surgery; thus, expanding the surgical indications. In this study, among the 122 patients with nipple discharge without any obvious space-occupying lesions in the lactiferous duct, such as extensive intraductal erosions, dark red bloody fluid or yellow serous fluid spillage at the opening of the terminal duct, extensive floccules, and fibrous network, 10.7% were diagnosed as having breast cancer by postoperative pathology, and there was no statistically significant difference in the detection rate of breast cancer compared to those with obvious space-occupying lesions in the lactiferous duct by FDS. This indicated that 10.7% of the patients who did not have space-occupying lesions in the mammary duct but had dark red bloody fluid or yellow serous fluid overflow or extensive erosion at the opening of the terminal duct would not be diagnosed as having breast cancer due to the absence of space-occupying lesions in the mammary duct by FDS. Therefore, on the basis of our double standards of surgical indication by FDS, the missed diagnosis rate of traditional surgical indication according to FDS could be further reduced.
Multiple intraductal papillomas, also known as papillomatosis, often occurred simultaneously in small ducts and terminal ductal lobular units, were prone to recurrence after surgery, and were prone to dysplasia and carcinogenesis. Mastectomy was feasible after the first operation in patients with dysplasia or radiation scars, and in patients with recurrence, it was necessary to guard against malignant transformation into breast cancer. In this group, two patients with multiple intraductal papillomas and radiation scars had malignant transformation into breast cancer eight months after the first operation.
Patients with no neoplasm seen by FDS often do not undergo surgery; thus, the false negative rate cannot be judged. In this study, 13 of the 122 patients with no obvious neoplasm seen by FDS were diagnosed as having breast cancer by postoperative pathology. These 13 patients had no neoplasm detected by FDS and could be regarded as patients with missed diagnosis by FDS. For those who had no neoplasm and had less spillage at the opening of the terminal catheter under FDS, it was likely that only clinical observation without surgery would be performed. Obviously, such breast cancer patients would be missed; thus, the actual diagnostic sensitivity for breast cancer would be less than 67.6%. The possible reasons for missed diagnosis were as follows: 1) complexity of the anatomy of the lactiferous duct system; 2) influence of the predilection site of breast cancer; 3) the limitation of fiberoptic ductoscopy itself; and 4) inconsistency in the operator's experience and endoscopic diagnostic criteria. For objective reasons, such as the complexity of lactiferous duct branches, the predilection site of breast cancer, and the limitation of fiberoptic ductoscopy itself, the localization and surgical methods in this study could be used to minimize the missed diagnosis rate of breast cancer, while for subjective reasons, such as the operator's experience, it can be repeatedly learned and summarized, especially to summarize the significance of the surgical indication criteria for patients without obvious space-occupying lesions under FDS. For example, in patients with extensive ductal erosion but no obvious space-occupying lesions, an experienced operator could diagnose this entity as highly suspected breast cancer.
Although mastoidectomy offered a minimally invasive modality, it was limited to when intraductal tumor foci were visible by FDS[8, 9, 10]. According to our experience, in patients without obvious space-occupying lesions by FDS, surgical treatment should be considered in the following situations: 1) intraductal papillomatosis of the breast was often associated with intraductal carcinoma, and terminal ductal hemorrhage or yellowish serous fluid could be seen in both breast cancer and intraductal papillomatosis; thus, surgical treatment should be performed in patients with unexplained hemorrhage or yellowish serous fluid in the distal duct; 2) in patients with severe intraductal inflammation and no clear space-occupying lesions, the lesion might be hidden under inflammatory floccules, and surgery was recommended; 3) active surgery should be performed in patients with extensive erosion of the ductal wall without clear neoplasm. In patients with pathologic nipple discharge, especially in those with no mass seen on physical examination and color Doppler ultrasound and negative mammography examination, FDS combined with methylene blue staining localization provided a method for early screening of breast cancer[11, 12].