MRI and pathological features of different molecular subtypes of breast cancers

Abstract

Objective To investigate the MRI and pathological features of different molecular subtypes of breast cancer.Methods The data of 202 patients who underwent primary breast cancer resection were retrospectively reviewed.All of the patients had MRI preoperatively.The molecular subtypes of breast cancer defined by immunohistochemistry were classified as basal-like,luminal and HER-2 overexpression.Morphology (including mass or non-mass like enhancement,shape and margin of masses,unifocal or multifocal masses) and enhancement characteristics on MRI,histologic types and grades of tumors were analyzed with Chi-square test,exact test,Fisher exact test,Kruskal-Wallis H test,and Wilcoxon test.Results Among the 202 patients,34 were basal-like,144 were luminal and 24 were HER-2 overexpression.The number of mass cases in each subtype was 29,133 and 19 respectively,making no significant difference (x2 =4.136,P =0.126).As for the shape of basal-like lesions,8 were round,19 were lobular and 2 were irregular,while this distribution was 23,58,52 in luminal subtype and 1,11,7 in HER-2 overexpression subtype (x2 =13.391,P ＜ 0.05).The margin was also strikingly different among three groups (smooth,spiculated,irregular):20,5,4 respectively in basal-like,27,53,53 respectively in luminal,and 4,7,8 respectively in HER-2 overexpression (x2 =28.515,P ＜ 0.01).52.6％ (10/19) of HER-2 overexpression cases were multifocal,while only 6.9％ (2/29) of luminal and 8.0％ (24/133) of basal-like ones were multifocal (x2 =16.140,P ＜ 0.01).Characteristics in dynamic contrast-enhanced MRI were statistically different,with homogeneous,heterogeneous,and rim enhancement 0,13,16 respectively in basal-like cases,28,93,11 respectively in luminal cases and 2,11,6 respectively in HER-2 overexpression cases (P ＜ 0.01).However,the difference for enhancement curve did not reach significance (P =0.457).Histologic types were significantly different among molecular subtypes (P ＜ 0.01).Luminal breast cancer consisted of various histologic types,32.6％ (47/144) of which were mixed type.The majority of the other two molecular subtypes were invasive ductal carcinoma.Furthermore,invasive ductal carcinomas with different molecular subtypes showed different histologic grades (Hc =30.014,P ＜ 0.01).Basal-like breast cancer was more likely associated with a higher grade of malignancy.Conclusions Different molecular subtypes of breast showed distinct MRI features and pathologic characteristics.MRI might be a useful tool for preoperative prediction of molecular subtypes of breast cancer. Key words: Breast neoplasms ; Magnetic resonance imaging; Pathology