•  Observational findings

The nipple morphology is most frequently everted (9 cases, 64,3%), less commonly flat (3 cases, 21,4%), and occasionally inverted (2 cases, 14,3%). Areolar and periareolar thickening of the skin occurs in 5 cases (35,7%) of the examined population. At MR, pathological nipples most commonly demonstrate SLE (57,1%) overlying a NEZ (50%), deep to which there is patchy (85,7%) or linear (14,3%) INE. INE appears to be the most common pattern of enhancement of tumor-infiltrated NAC (Figure 4, 5, 6). At independent assessment of INE kinetics, the majority of nipples (57,1%) show a persistent enhancement pattern, with marked intensity being the most common; only 1 patient have mild intensity INE enhancement (7%) (Figure 7, 8). The most represented MR INE pattern is patchy, while linear pattern is observed only in 2 patients. 2 patients with “nodular” patchy INE are affected by multicentric G3 (high grade) IDC (invasive ductal carcinoma). The observational findings are resumed in Table 1.

• Radiologic Correlation between MR and CT findings

NAC enhancement in CT scans acquired in the venous phase is found in 13 cases (92,9% of the population). The most frequent combination of CT enhancement patterns involves base (13) + body (10) of the nipple (71,4%) (Figure 9, 10). When NEZ is not interested by the tumor in MR imaging (7 cases), usually CT scans demonstrate the enhancement of the base and the body (4 cases, 57%) or of the base of the nipple alone (2 cases, 29%). CT images have less sensitivity compared to MR in the detection of SLE (5 cases, which are patients with nipple thickening) (Figure 11, 12).

• PET/CT outcomes: NAC-SUV ratio

We measured with a quantitative modality SUV values for the NAC in the malignant breast and the contralateral normal breast (Figure 6). We calculated the NAC-SUV considering the ratio between SUV of the NAC in the malignant breast / SUV of the NAC in the contralateral normal breast. The NAC-SUV was calculated for early phase images. The average value of SUV of pathologic NACs is 3,84, the average value of SUV of contralateral normal NACs is 2,25. The average NAC-SUV ratio is 1,7. Quantitative parameters derived from PET/CT, such as early phase SUV ratios of pathologically involved NACs compared to the contralateral normal breast, can offer significant predictive value for determining NAC involvement.