## 4 Discussion  
As far as we know, this is the first time that a SGL after a GL has been utilized for the evaluation of PND patients. The results obtained provide evidence that SGL combined with GL improves diagnostic efficiency, especially of borderline and malignant lesions. These findings are fundamental for establishing the differential diagnosis between benign, borderline, and malignant lesions. The physical examination was negative in all the patients in the present study, and the cytology of the nipple discharge was negative in the two cases where it was performed. The physical examination, MMG, and US, are the first-line methods for evaluating PND. Considering the various types of imaging methods utilized for the management of women with PND, it is fundamental to establish standardized diagnosis algorithms for better efficiency [9,10,20,24]. In this sense, when the conventional image examination (MMG and US) is negative, the GL is considered a fundamental procedure for the diagnosis of PND, as it provides precise information for the localization of the lesions, and it is used as a guide for the planning of surgery [5,8,9,10,20]. Likewise, the GL is a simple, cheap, and fast technique which takes about 15 min [8,9,20,25]. Likewise, the GICS classification system [15] is a useful tool for differentiating between benign and malignant lesions. In addition, with the application of an anesthetic cream in the areola-nipple area, the patients tolerate the procedure well [22]. In the cases of extravasation or failure of the technique, repeating the GL is recommended again after one or two weeks. Despite all the advantages of GL, it is an underutilized technique. We believe, in agreement with other authors [8,9,20,25], that GL is not an obsolete technique and should be utilized as a second-line diagnostic procedure in PND. In addition, it is important to perform a SGL after the GL so that the intraducted lesions without ductal ectasia can be evaluated, which in the DCIS cases are very small (<3 mm) and cannot be observed with conventional imaging methods. In the present study, the findings that were most frequently observed in the GL were filiform ducts with microdefects (Figures 4 and 5), which in the SGL corresponded to micronodules and badly-defined duct walls. In these cases, it is important to take into account the identification of the problem duct, which can be observed with the contrast dye as anechoic, and could have an aspect of small hyperechoic foci or with a hyperechoic continuous intraductal content. Based on our experience, the SGL is a complementary test to the GL which allows for the precise localization of small intraductal lesions as well as their characterization. In this way, the differentiation between benign, borderline, and malignant lesions can be improved. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & & & & \\ \hline \multicolumn{6}{c}{**Borderline + Malignant**} \\ \hline  & Acc \% (95\% CI) & Se \% (95\% CI) & Sp \% (95\% CI) & PPV \% (95\% CI) & NPV \% (95\% CI) \\ \hline \multirow{2}{*}{Galactography} & 90.2 & 100 & 68.75 & 87.5 & 100 \\  & (77.8–96.3) & (87.7–100) & (41.5–87.9) & (72.4–95.3) & (67.9–100) \\ \multirow{2}{*}{Songgalactography} & 100 & 100 & 100 & 100 & 100 \\  & (91.3–100) & (87.7–100) & (75.9–100) & (87.7–100) & (75.9–100) \\ \hline \multicolumn{6}{c}{**Malignant**} \\ \hline  & Acc \% (95\% CI) & Se \% (95\% CI) & Sp \% (95\% CI) & PPV \% (95\% CI) & NPV \% (95\% CI) \\ \hline \multirow{2}{*}{Galactography} & 96.08 & 100 & 95.35 & 80 & 100 \\  & (85.4–99.3) & (59.8–100) & (82.9–99.2) & (44.2–96.5) & (89.3–100) \\ \multirow{2}{*}{Songgalactography} & 96.08 & 100 & 95.35 & 80 & 100 \\  & (85.4–99.3) & (59.8–100) & (82.9–99.2) & (44.2–96.5) & (89.3–100) \\ \hline \hline \end{tabular}  
* PPV: positive predictive value, NPV: negative predictive value; Acc: accuracy; Se: sensitivity; Sp: specificity.  
\end{table} 
Table 3: Diagnostic efficiency of the galactography and the sonogalactography.