Breast Ultrasound

Breast ultrasound uses high frequency sound waves to make images of the breast, the axilla and the chest wall. It is the first test for breast symptoms in women under 30 to 40, in pregnant and breast feeding women, and it is the usual tool to assess a lump seen on mammography.

It tells a solid mass from a cyst and describes features that separate benign and malignant lesions. It also directs needle biopsy and the placement of wires or markers.

A linear probe of 7.5 to 18 MHz is used with the patient supine, and the arm raised over the head. The breast is scanned in radial and antiradial planes, in a systematic way, from nipple to periphery, with the axilla included.

Automated whole breast ultrasound is available in some centres. Colour Doppler shows vascularity, and elastography measures stiffness.

There is no ionising radiation. Sensitivity for symptomatic masses is about 90 to 95% in experienced hands. When added to mammography in women with dense breasts, it finds a further 2 to 4 cancers in each 1000 women screened, but more false positive results occur.

Indications.

• Palpable breast lump, pain that is focal, nipple discharge, skin change or breast inflammation.
• Women under 30 to 40 with symptoms (first test).
• Pregnant and breast feeding women with symptoms.
• Assessment of a mass or asymmetry seen on mammography or tomosynthesis.
• Distinction of a cyst from a solid mass.
• Dense breasts, as a supplement to mammography in screening.
• Axillary lymph nodes, to stage breast cancer and direct node sampling.
• Breast infection, abscess and drainage.
• Implants: checking for rupture, collections and complications.
• Direction of biopsy, localisation of lesions before surgery, and follow up of known lesions.
• Men with breast enlargement or a lump.

Contraindications and precautions.

• No absolute contraindications. It is safe in pregnancy and lactation.
• A clean skin is needed, and open wounds are covered.
• Pain in the breast can limit the pressure that can be used.
• Large breasts and breasts with fatty tissue need more time and good technique.
• Operator experience strongly affects the result. Incomplete scanning can miss lesions.
• A negative ultrasound in a patient with a suspicious mammogram does not exclude cancer.
• Biopsy is needed for suspicious lesions. Anticoagulants are noted before needle sampling.
• A chaperone should be offered as local practice requires.

Preparation and technique.

No preparation is needed. The patient lies supine, with the arm behind the head, and turned slightly so that the breast is spread. A warm gel is applied.

The probe is moved in overlapping lines over the whole breast and the axilla. The site of any palpable lump is scanned directly, and the position is recorded by clock face and distance from the nipple.

Each lesion is measured in three planes, and described by shape, orientation, margin, echo pattern, posterior features, calcifications and vascularity. Elastography adds a stiffness estimate.

Images are saved with annotations. Axillary nodes are measured, and the cortex and hilum are described.

Normal appearances.

The skin is a thin bright line. Under it lie fat (dark grey), glandular tissue (bright and mixed), and ducts converging to the nipple. Cooper ligaments appear as thin bright lines, and the pectoralis muscle and ribs lie behind the breast.

Normal axillary nodes are oval, with a thin cortex (under 3 mm) and a bright fatty hilum.

Interpretation.

• Simple cyst: round or oval, anechoic, with a thin wall and posterior enhancement. It is benign and needs no further action unless symptomatic.
• Complicated cyst: low level internal echoes, with no solid component. Usually benign, with follow up or aspiration if it is symptomatic.
• Complex cystic and solid mass: a cyst with thick walls, thick septations or a solid nodule. It needs biopsy.
• Benign solid mass: oval shape, parallel (wider than tall) orientation, circumscribed margin, uniform echoes, thin capsule. Fibroadenoma is the most frequent.
• Suspicious mass: irregular shape, non-parallel (taller than wide) orientation, spiculated or angular margins, hypoechoic with posterior shadowing, calcifications, and increased vascularity. Elastography shows increased stiffness.
• Ductal changes: dilated ducts with an intraductal mass suggest papilloma or ductal carcinoma in situ.
• Abscess: a thick walled fluid collection with debris and surrounding oedema.
• Axillary nodes: cortical thickening over 3 mm, loss of the fatty hilum, and round shape are suspicious.
• Implant rupture: multiple parallel lines within the implant (intracapsular) or echogenic noise with dense posterior shadowing outside it (extracapsular).
• Findings are placed in the categories used for mammography.

Critical values and findings needing immediate action.

• Findings highly suggestive of cancer: core biopsy and referral to a breast service within days.
• Breast abscess: drainage and antibiotics.
• Inflammatory changes with skin thickening: urgent assessment for inflammatory cancer.
• New mass in pregnancy or lactation: biopsy if suspicious.
• Haematoma with a rapidly enlarging breast after biopsy: compression and surgical review.

Limitations and artefacts.

• Operator dependence is high, and whole breast examination is time consuming.
• Microcalcifications and some ductal carcinoma in situ are poorly shown. A negative ultrasound does not remove the need for mammography.
• Deep lesions in large breasts, and lesions near the chest wall, are hard to image.
• Fat lobules, ribs, Cooper ligaments and normal shadowing can mimic masses.
• Posterior shadowing from scars and dense tissue hides lesions.
• Cancers can look benign (circumscribed, with posterior enhancement), such as mucinous and medullary types.
• Supplemental screening causes more false positive results and biopsies.
• Elastography depends on the amount of pressure.
• Cysts sometimes contain debris and look solid.
• Implants shadow the tissue behind them.

Special groups.

• Women under 30 to 40: first test, with mammography only if needed.
• Pregnant and breast feeding women: first test, and safe.
• Women with dense breasts: supplement to mammography.
• Women with implants: used for rupture, collections and complications.
• Men: gynaecomastia is usual, and a hard eccentric mass needs biopsy.
• Children and adolescents: breast buds and fibroadenomas are usual.
• Regions: ultrasound is often the only imaging test available. Clinical examination, ultrasound and core needle biopsy are the main approach.

Follow up tests.

• Digital mammography or tomosynthesis.
• Breast MRI.
• Contrast enhanced mammography.
• Core needle biopsy or vacuum assisted biopsy.
• Fine needle aspiration of a cyst or an axillary node.
• Short interval repeat ultrasound at 6 months for probably benign lesions.
• Referral to a breast surgeon, oncologist or breast clinic.