Nipple discharge accounts for 2–10% of the symptoms that women complain when they seek care at breast clinics and it is an alarming sign for both patients and clinicians since it may present sign of breast cancer . In the evaluation of PND, the limitations of sonomammography and galactography have led to further research on complementary methods such as MRI and ductoscopy . So, in the workup and management of nipple discharge, conclusions drawn about the diagnostic utility of MRI .
Our study found that benign diseases (74.2%) were the most common cause of pathologic nipple discharge, while we found high risk lesion and malignancy rate in (25.8%) of cases. Paula et al.  reported that the most common causes of nipple discharge were some benign breast lesions, such as ductal ectasia, in 6–59% of cases, and papilloma, in 35–56%. The risk of underlying malignancy is not negligible, ranging from 5 to 23%. In the current study, most (72.3%) of bloody nipple discharge was due to underlying malignant causes. Chen et al.  stated that there is association between the color of nipple discharge and breast cancer risk.
In our study, the mammographic findings in patients were as follows: asymmetric densities, dilated duct in sub areolar region, masses, and micro calcifications. Ballesio et al.  reported that mammography in patients with nipple discharge was negative in 60% of cases and also reported that the positive mammographic findings include asymmetric density, duct ectasia, and calcification.
The most common ultrasonographic features in this study were simple dilated ducts or duct ectasia with intraductal internal echoes. Ballesio et al.  found that the most common sonographic features in pathologic nipple discharge were duct dilatation, particularly associated with internal echoes and duct wall thickening. In our study, papilloma and papillomatosis on ultrasonography appeared as retroareolar dilated duct with intraductal solid internal echoes. Mammography showed no abnormality, asymmetric density, retroareolar dilated ducts, and calcification. Eiada et al.  reported that small papilloma can be occult in mammography, particularly when located in the retroareolar regions because of the breast density and relative lack of compression in that area. Dhull et al.  reported that intraductal papillomas were seen as intraductal mass lesions in all patients on sonography and MRI, while were seen in only three patients (43%) on mammography.
Lam et al.  found on US examinations dilated ducts associated with (21.7%) of their detectable papillomata. A dilated duct is a sonographic sign useful for differentiating intraductal lesions from other benign lesions such as fibroadenoma. Papilloma may present as a circumscribed hypoechoic oval nodule. In this study, papilloma on MRI appeared as enhanced focus, enhanced mass, and non-mass enhancement with different kinetics making differentiation between papilloma and carcinoma is somewhat difficult. However, previous studies reported some overlaps in MRI findings between papilloma, papillomatosis, and carcinoma [10, 13].
As regard malignant causes of pathologic nipple discharge, mammographic findings of DCIS in our study were suspicious masses, focal asymmetry with or without calcifications. Yamada et al.  reported mass, asymmetries, and micro calcification in mammogram of DCIS. In our experience, ultrasonographic findings in DCIS were mottled/heterogeneous parenchyma with increased vascularity on Doppler, multiple intra cystic solid masses, and peripheral dilated ducts with irregular wall and echogenic contents. Watanabe T et al.  found that the most frequent ultrasonographic findings in DCIS were hypoechoic areas, followed by solid masses, abnormalities of the ducts or mixed masses, distortion, multiple small cysts, and echogenic foci without a hypoechoic area also were reported. The ultrasound features of DCIS have been described in the literature; however, the classifications vary slightly among authors. Ultrasound images of DCIS have been classified into masses, calcification alone, ductal change, and architectural distortion [16,17,18,19,20]. In our study, MRI findings of DCIS were retroareolar region of high signal intensity on T2WI, on dynamic post contrast study, diffuse non-mass enhancement with clustered ring pattern, segmental non-mass enhancement with clumped pattern, and regional non-mass enhancement. The extension of enhancement pattern was very close to the actual involvement of breast parenchyma by malignancy in correlation with pathology. So we found that MRI is valuable not only in diagnosis of DCIS but also for detection of actual extent of DCIS. Several reports [21, 22] found that DCIS most commonly appears as a non-mass enhancement (60–81%), and less frequently as a mass (14–41%) or a focus (1–12%). Nori et al.  compared the mean absolute error between preoperative MRI and mammography evaluations and final disease extent; MRI showed an improved accuracy of 51.2%. Study done by Hajaj et al  suggests that MRI could be an important tool in reducing the re-excision rates in the surgical management of high-grade DCIS.
In our experience, most of the infiltrating duct carcinoma cases were (IDC) associated with DCIS, and most cases were detected by mammogram and ultrasound, apart from few cases which were negative by mammogram due to dense parenchyma. Their appearance on US included irregular-shaped mass(es) with non-circumscribed margin and the remaining cases showed slight increase in echogenicity at the operative bed with nearby fluid collections and were categorized as BIRADS3 (postoperative change) as patients underwent unplanned resection for a mass. On MRI, all cases were detected, so MRI was valuable in detecting missed malignancy especially in dense parenchyma.
Bahl et al.  demonstrated that breast MRI is a valuable additional diagnostic tool in the setting of negative conventional imaging. In addition, a negative MRI in this symptomatic population may obviate the need for invasive surgery. Meta-analysis study done by Houssami et al.  reviewing 19 studies of women with breast cancer found that MRI detects additional disease in 16% of women. Regarding MRI feature of IDC with DCIS, all masses were irregular in shape with non-circumscribed margin and they showed either heterogeneous or rim enhancement with associated non-mass enhancement of clumped pattern on post contrast study. Apple et al.  concluded that invasive ductal carcinoma on post contrast study appeared as enhanced irregular shaped mass with non-circumscribed margin, or may appear as non-mass enhancement.
In our study, sensitivity and specificity of mammogram and ultrasound in diagnosing cases with pathologic nipple discharger was 71.4% and 54.2% respectively, while sensitivity and specificity of MRI was 100% and 83.3%. In a study done by Yılmaz R et al. , the sensitivity of US was found higher in the identification of intraductal lesions than that in the literature [20, 21]. This study revealed sensitivity and specificity for US as 75% and 66.7%, respectively. Ohlinger R et al.  reported a sensitivity of 82.9%, higher than study done by Yılmaz R et al. , but they calculated a specificity of 17.9%, which was lower than many studies. Ohlinger R et al.  study was multicentered, so it is difficult to standardize diagnostic criteria; this high rate of sensitivity could in part be due to broad positive findings (e.g., cystic lesions and ductal ectasia). Study done by Yılmaz R et al.  showed that US sensitivity and specificity can be higher if used specifically for ID pathologies and PND.