Additional occult cancers identified on staging breast MRI: imaging appearances and pathologic characteristics

Abstract

Introduction: Breast magnetic resonance imaging (MRI) is increasingly being used for staging of patients with breast cancer due to its high sensitivity in detecting additional cancers (ACs). However, the clinical impact of diagnosing and treating these cancers remains unclear.

Methods: A retrospective study was undertaken of patients with newly diagnosed breast cancer who underwent staging MRI at The American University of Beirut Medical Centre (AUBMC) between 2012 and 2020. Pathology reports and breast MRI examinations were reviewed. Eighteen breast cancer patients with 19 pathology-proven index cancers (ICs) and 19 pathology-proven MRI-detected ACs were included. Chi-square and Fisher's exact tests for categorical variables and Wilcoxon signed rank test for numerical variables were used to compare ICs to ACs.

Results: The ICs consisted of four ductal carcinoma in situ (DCIS), 13 invasive ductal carcinomas (IDC), of which five with associated DCIS, and two invasive lobular carcinomas, (ILC) of which one with associated DCIS. ACs comprised 12 DCIS, five IDC, two with associated DCIS and two ILC, one with associated DCIS. Interval cancers were more frequently invasive whereas ACs were more frequently in situ (P = 0.021). ACs were more frequently nuclear grade 2 (P = 0.009). There was no statistically significant difference between ICs and ACs in lesion type (P = 0.062), shape (P = 0.073), initial enhancement (P = 1), delayed enhancement (P = 0.732), hormonal receptor profile (P = 0.68) and Ki67 (P = 0.388). Among ACs, ten (53%) were larger than 10 mm of which five (26%) were invasive cancers, and five (26%) were larger than the ICs.

Conclusions: ACs detected by breast MRI were more likely to be in situ and to show a nuclear grade 2. Although not reaching statistical significance, some ACs tend to be clinically significant by their type, size or nuclear grade. The impact on clinical management remains to be determined.

Keywords: breast MRI; breast cancer; pathology; staging.

Figure 1

A 62‐year‐old lady with a newly diagnosed left breast grade 3 invasive ductal carcinoma, (short arrow). Multiple other lesions were identified within the same quadrant several of which were located farther than 4 cm from the index mass. The most distant mass was biopsied (long arrow), pathology shows a grade 3 invasive ductal carcinoma.

Figure 2

A 73‐year‐old lady with a recent diagnosis of right breast grade 2 invasive lobular carcinoma (short arrow). Staging breast MRI shows in addition another irregular mass in the contralateral breast with no correlate on conventional imaging. MRI guided biopsy shows a grade 2 invasive lobular carcinoma (long arrow).

Figure 3

A 44‐year‐old lady with a recent diagnosis of grade 1 invasive ductal carcinoma (IDC) identified as an area of architectural distortion on screening mammography (circle). The staging MRI shows the index mass in the upper outer quadrant with a clip within it (short arrow), but also reveals extensive non‐mass enhancement in the lower outer quadrant. MRI guided biopsy shows grade 1 IDC and extensive ductal carcinoma in situ.

Figure 4

A 42‐year‐old lady with recently diagnosed right breast grade 3 ductal carcinoma in situ (short arrows), appearing as clumped non mass enhancement in the lower outer quadrant. The staging MRI shows in addition an irregular homogenous subareolar mass (long arrow), pathology shows a grade 2 invasive ductal carcinoma.

Figure 5

A 47‐year‐old lady with a recent diagnosis of grade 1 invasive ductal carcinoma (IDC) and ductal carcinoma in situ (DCIS) in the upper outer quadrant of the left breast (short arrow). The staging MRI shows in addition extensive non mass enhancement in the central subareolar breast. MRI guided biopsy reveals grade 2 IDC and extensive DCIS (long arrows).