MRI features of mucinous carcinoma of the breast: correlation with histopathology

Abstract

Objective To characterize the features of breast mucinous carcinoma on T2WI, dynamic contrast-enhanced MR imaging (DCE-MRI) and diffusion weighted imaging (DWI) and correlate the MR features with histopathology. Methods MR imaging in 8 women (aged 33--65 years old) with mncinous carcinoma of the breast verified histopathologically was performed on 1.5 T scanner with T1WI, FS T2 WI, 3D DCE-MRI using volume imaging for breast assessment(VIBRANT) sequence, DWI with b value of 500 and 1000 s/mm2 by single-shot EPI sequence. According to the lexicon of BI-RADS-MRI designed by ACR, the MR findings were retrospectively studied, including morphology, signal intensity on T1WI and FS T2WI, mass enhancement, the patterns of dynamic enhancement curve, and the mean ADC on DWI. The pathologic diagnosis was made according to the standard criteria by the World Health Organization Classification of Tumors. Results Five patients were pure mucinous carcinoma and 3 patients were the mixed. The amount of mucus ranged from 60% to 90%. All 8 tumors presented as a mass on MRI with low signal intensity on T1WI, high or strongly high signal intensity on FS T2WI and high signal on DWI. The tumor size ranged from 1.3 to 3. 2 cm in diameter. Five tumors showed rim enhancement in early phase and the central part was gradually enhanced in delayed phase. One tumor presented slightly heterogeneous enhancement. Two tumors showed progressively heterogeneous enhancement. The mean ADC values of tumor were (2.41±0.28) ×10-3 mm2/s with b value of 500 s/mm2 and (2.06 ±0. 14) × 10-3 mm2/s with b value of 1000 s/mm2, and higher than that of the normal breast tissue [ ( 1.71 ±0. 32) × 10-3 and ( 1.43 ± 0. 24) × 10-3 mm2/s]. Conclusions The MR features of breast mucinous carcinoma on T1WI, DCE-MRI, and DWI are different from that of invasive ductal carcinomas and may reflect its distinct histological type. The combination of these MR sequences may lead to a pre-operative diagnosis of this tumor. Key words: Breast neoplasms; Diffusion magnetic resonance imaging