Background parenchymal enhancement in pregnancy-associated breast cancer: a hindrance to diagnosis?

Abstract

The purpose of this study is to investigate the detectability of pregnancy-associated breast cancer (PABC) in lactating glandular tissue on magnetic resonance imaging (MRI) by using pre- and post-contrast acquisitions and their derived postprocessed images and compare these results to ultrasound (US) and mammography (MG). We reviewed the electronic database for women with PABC and existing breast MRI. MR images (T2-weighted short inversion-recovery sequence [STIR], dynamic contrast-enhanced T1-weighted gradient echo sequence and postprocessed subtraction images [early post-contrast minus pre-contrast]) were retrospectively evaluated (image quality, parenchymal/tumour enhancement kintetics, tumour size and additional lesions). Supplemental subtraction images (latest post-contrast minus early post-contrast) to reduce plateau enhancement were additionally calculated and tumour conspicuity and size were measured. Findings were compared to US and MG reports. Nineteen patients (range 27-42 years) were included. Background parenchymal enhancement (BPE) was minimal (n=1), mild (n=3), moderate (n=7) and marked (n=8) with kinetics measured plateau (n=8), continuous (n=10) and not quantifiable (n=1). Tumour kinetics presented wash-out (n=17) and plateau (n=2). Eighteen of nineteen tumours were identified on the supplemental subtraction images. All tumours were visible on US; 12/19 were visible on MG (63.2%). MRI detected additional malignant lesions in two patients. Despite high BPE of the lactating breast, MRI securely detects carcinomas and identifies satellite lesions. By using supplemental subtraction images, background enhancement can be eliminated to facilitate diagnosis. US remains a reliable diagnostic tool, but additional MRI is recommended to rule out satellite/contralateral lesions. MG interpretations can be difficult due to high parenchymal density. • Despite high background enhancement, MRI of the breast confidently detects carcinomas and identifies further lesions in the lactating breast. • By using supplemental subtraction images, background enhancement in the lactating breast can be eliminated to facilitate diagnosis. • US remains a reliable diagnostic tool. Mammography can be limited due to extremely dense breast tissue related to lactation.