Introduction
This topic covers imaging of breast lesions: which modality to use for screening, diagnosis and staging, how benign and malignant tumors look on mammography, ultrasound and MRI, and how findings are standardised and acted upon. For the exam, the key idea is that imaging classifies a lesion and decides whether tissue sampling is needed; it rarely gives a final histological diagnosis on its own.
Imaging modalities
- Mammography is the screening method of choice in women aged about 40 to 74. Two standard views are taken of each breast: craniocaudal (CC) and mediolateral oblique (MLO). Digital mammography and digital breast tomosynthesis (3D) improve detection, especially in dense breasts.
- Ultrasound is the first-line test for palpable lumps in young women and for characterising lesions seen on mammography. It separates cystic from solid lesions, is the main tool for the axilla, and guides biopsy.
- MRI with dynamic contrast enhancement is the most sensitive modality. It is used for screening high-risk women (for example BRCA mutation carriers or strong family history), for assessing disease extent and multifocality, for checking implant integrity, and for solving discordant findings. Its drawbacks are false-positive enhancement and cost.
- Ductography (galactography) injects contrast into a duct to localise the cause of single-duct nipple discharge. It has largely been replaced by ultrasound and MRI of the ducts.
- Image-guided biopsy (core needle, vacuum-assisted, under ultrasound, stereotactic or MRI guidance) is the standard way to obtain a histological diagnosis. Surgical excision is reserved for lesions that cannot be sampled reliably or for discordant results.