What is the initial imaging modality of choice for a patient presenting with a new breast lump, considering age and other risk factors?

Initial Imaging for New Breast Lump

For women ≥40 years old, obtain diagnostic mammography (or digital breast tomosynthesis) first, followed by targeted ultrasound in most cases; for women <30 years old, start with ultrasound; for women 30-39 years old, either modality is acceptable as the initial study. 1

Age-Based Imaging Algorithm

Women ≥40 Years Old

• Diagnostic mammography or digital breast tomosynthesis (DBT) is the mandatory first imaging study 1
• The sensitivity of mammography alone ranges from 86% to 91% in this age group 1
• Mammography must include standard mediolateral oblique and craniocaudal views of both breasts to screen for additional occult lesions 1, 2
• A radio-opaque marker should be placed on the skin over the palpable finding to identify its location 1
• After mammography, targeted ultrasound should be performed in most cases to further characterize the palpable finding, unless mammography shows a clearly benign correlate (oil cyst, hamartoma, degenerating fibroadenoma, lipoma, benign lymph node) 1, 3

Women <30 Years Old

• Ultrasound is the initial imaging modality of choice 1, 4
• This recommendation is based on the low incidence of breast cancer (<1%) in this age group and the theoretically increased radiation risk of mammography 1
• Most benign lesions in young women are not visualized on mammography 1
• Neither diagnostic mammography nor DBT is recommended as the initial imaging modality in this age group 1

Women 30-39 Years Old

• Either ultrasound or diagnostic mammography/DBT can be used as the initial imaging evaluation 1, 4
• The sensitivity of ultrasound may be higher than mammography for women younger than 40 years (95.7% vs 60.9% in one study of 1,208 women aged 30-39) 1
• Use a low threshold for adding mammography if clinical examination or other risk factors are concerning 1
• If a suspicious mass is identified on ultrasound in this group, bilateral mammography is recommended 1

Critical Rationale for This Approach

Why Diagnostic Mammography (Not Screening) for ≥40 Years

• Diagnostic mammography provides global assessment of both breasts to detect synchronous cancers that would alter surgical planning 2
• It identifies microcalcifications and subtle architectural distortion that may indicate ductal carcinoma in situ (DCIS), features often not well seen on ultrasound 1, 2
• Spot compression views with or without magnification or tangential views are obtained to specifically evaluate the clinical finding 1
• DBT can be used as an alternative, with equivalent or better diagnostic accuracy than supplemental diagnostic mammographic views 1

Why Ultrasound First for <30 Years

• Ultrasound allows direct correlation between the palpable abnormality and imaging findings 4
• It immediately determines if a breast mass is a fluid collection, solid mass, or complex lesion 4
• The combined negative predictive value of mammography with ultrasound ranges from 97.4% to 100% 1, 2
• Ultrasound has very high sensitivity in younger women without radiation exposure 4, 5

Essential Sequencing Principles

Complete Imaging Before Biopsy

• A thorough imaging workup of a palpable mass must be completed prior to biopsy 1, 4, 2
• Changes related to biopsy may confuse, alter, obscure, and/or limit subsequent image interpretation 1, 4

When to Proceed to Biopsy

• If imaging shows a suspicious correlate, proceed to image-guided core biopsy (preferred over fine-needle aspiration) 1, 2
• Any highly suspicious breast mass detected by palpation should be biopsied, regardless of negative imaging findings 1
• For ultrasound-visible suspicious lesions, ultrasound-guided biopsy is preferred even for palpable findings 4, 6

Special Populations

Pregnant or Lactating Women

• Ultrasound is the first modality for investigation of a lump 1, 3, 7
• Tissue density limits mammographic evaluation in lactating women 1
• Mammography is not contraindicated during pregnancy or lactation and should be performed if malignancy is suspected 1, 7
• Mammography has 90-100% sensitivity for malignancy when performed preoperatively in pregnant/lactating patients with known cancer 1

Common Pitfalls to Avoid

• Do not order routine screening mammography for a palpable lump—diagnostic mammography with targeted views is required 1
• Do not rely solely on physical examination, as experienced examiners agreed on the need for biopsy in only 73% of 15 masses subsequently proven malignant 1, 4
• Do not use MRI, PET, or molecular breast imaging in the routine initial evaluation—there is no role for these advanced technologies 1, 3, 5
• Do not skip mammography in women ≥40 years even if ultrasound is planned, as mammography may detect occult disease or microcalcifications 1, 2
• Never allow negative imaging to overrule a strongly suspicious physical examination finding 1, 4