[Breast cancer subtypes based on ER/PR and Her2 expression: comparison of MR imaging features]

To evaluate the magnetic resonance (MR) imaging findings of breast cancer subtypes based on the profiles of ER/PR and Her2.

A retrospective study was conducted for 267 breast cancer subjects between February 2007 and January 2011. Clinicopathologic features and MR imaging findings of four subtypes were compared. The Chi-square (χ(2)) test, Fisher's exact test and χ(2) section method were employed for categorical variables.

MR imaging findings:Patients with segment or linear enhancement type accounted for 25.6% in ER/PR(+), Her2(+) subtype group and 36.1% in ER/PR(-), Her2(+) subtype, no significant difference existed between them (χ(2) = 1.112, P = 0.641). But they were significantly higher than ER/PR(+), Her2(-) subtype group and ER/PR(-), Her2(-) subtype group (χ(2) = 32.793, P < 0.001; χ(2) = 14.565, P < 0.001). ER/PR(-), Her2(-) subtype patients accounted for 14.6% of the total breast cancer patients (39/267). Subjects with ER/PR(-), Her2(-) subtype were more likely to present unifocal (91.7%, 33/36) and mass type lesion (92.3%, 36/39). The mass type lesions in ER/PR(-), Her2(-) subtype group were more likely to showed smooth margin [58.3% (21/36), P < 0.001], very high intratumoral signal and peripheral hyperintense pattern on fat suppression T2-weighted imaging (P < 0.001) and early rim enhancement [81.5% (29/36), P < 0.001]. No significantly difference of four subtypes were found on number of mass, mass shape and pattern at dynamic enhancement imaging (χ(2) = 1.413, P = 0.713; χ(2) = 8.423, P = 0.204; χ(2) = 4.657, P = 0.540).

Segment or linear enhancement type is characterized by MR imaging. Early rim enhanced mass is ER/PR(-), Her2(-) breast cancer. The most important characteristics of MR imaging include a smooth edge of breast mass, very high intratumoral signal on fat suppression T2-weighted imaging and peripheral hyperintense pattern.