Teaching Case

At first mammography, two no palpable suspicious lesions were detected at external upper quadrant of the right breast. A high-frequency ultrasound (13 MHz) examination by the same radiologist was performed, even for a possible biopsy. However, a discordance between mammography and ultrasound resulted shifting the patient evaluation to MR imaging.

In a 41-year-old woman, clinical breast examination, mammography, and ultrasound were discordant. In particular, clinical examination was negative, mammography showed two lesions of 13 and 9 mm in diameter at the upper external quadrant of the right breast (Figs 1-2) while ultrasound confirmed only the 13-mm lesion and revealed a third lesion of 10 mm in diameter at the conjunction of the internal quadrants of the same breast (images not shown), not visible at mammography, either retrospectively. A 1.5-T MR examination without and with intravenous administration of 0.1 mmol/kg of gadobenate dimeglumine was performed, showing a total of four suspicious enhancing foci in the right breast (Figs 3-4). After MR, a “second look” ultrasound was performed, allowing the detection of one lesion previously undetected at the first look ultrasound. An ultrasound-guided core biopsy of the largest lesion at the upper external quadrant was performed; moreover, the remaining two lesions visible at ultrasound were localized using a suspension of vegetable charcoal. On the basis of all imaging studies, the surgical intervention was planned, including preliminary pathological examination during surgery: right mastectomy was finally performed, including careful excision of the lesion between the pectoral muscles.

Preoperative staging is one of the major indications to contrast-enhanced MR imaging of the breast. The aims are the accurate evaluation of the index tumor size and possible involvement of skin, pectoral muscle or chest wall, as well as the detection of an extensive intraductal component, of multifocality or multicentricity, of contralateral malignant lesions [1]. In the detection of multiple malignant foci, MR imaging was demonstrated to be higher sensitive than mammography in multiple studies. In particular, also using the whole excised breast as a standard of reference, mammography achieved a significantly lower sensitivity (66%) for malignant foci compared with MR (81%) [2]. If the clinical aim is the detection of multicentricity (which surely changes the surgical planning) the comparison between MR imaging and mammography is greatly in favor of the former: in a recent study, the ability to depict multicentricity was reported to be 95% for MR imaging and only 15% for mammography [3]. The role of ultrasound in detection of multiple malignant breast is under investigation; however, MR imaging was reported to be more sensitive than the combination of mammography and ultrasound [4] in detecting multiple breast cancer foci, as it was for the case here presented. However, for this patient the diagnosis of multifocal disease was established already with mammography and multicentric disease was established at the first look ultrasound. Notably, MR only imaging showed the entire disease extent (four foci, one of them undetectable at mammography, first and second look ultrasound, located between the pectoral muscles, interpreted as a probable metastasis of a Rotter’s lymph node). This last finding demonstrated that the diagnosis of multicentric disease at conventional imaging could not be enough for a well-tailored treatment planning and local staging. In fact, for the former a mastectomy had to be extended to include interpectoral lymph nodes; for the latter, as demonstrated in the Kaplan-Meier survival study, the designation of grade N3 of the TNM classification should be considered in case of interpectoral lymph node involvement [5]. By the way, taking into account that a high-relaxivity contrast agent [6] was used, the absence of false positive findings should be positively evaluated. In fact, false positives of breast MR imaging are the current reason of concern for surgeons and oncologists (for the possible shift from breast conserving surgery to unnecessary mastectomy) and make MR-guided biopsy mandatory when only MR-detected enhancing foci are in favor of a multicentric cancer [7].