Introduction
This presentation provides a comprehensive, practice-oriented review of evaluating the male breast, emphasizing the predominance of benign conditions—especially gynecomastia—while detailing the rare but important spectrum of malignancies. It aligns diagnostic pathways with the American College of Radiology (ACR) Appropriateness Criteria, outlines modality-specific roles and pitfalls, describes classic imaging appearances, and concludes with tailored considerations for transgender patients.
Epidemiology and Clinical Context of Male Breast Disease
Male breast presentations are common in diagnostic breast centers, with most attributable to benign etiologies, particularly gynecomastia. Male breast cancer constitutes approximately 1% of all breast cancers in the U.S. (<2,000 cases annually), with incidence increasing with age. Stage-for-stage survival parallels that in women, but men often present later, leading to worse outcomes.
Key Points
- Benign causes predominate; gynecomastia is most common
- Male breast cancer: <1% of all breast cancers; median age ~67
- Later-stage presentation is typical due to lack of screening and awareness
- Nodal metastasis at diagnosis portends worse prognosis
ACR Appropriateness Criteria: Purpose and Scope
The ACR Appropriateness Criteria were developed to standardize imaging decisions across clinical scenarios using expert consensus and periodic updates. They provide practical guidance for modality selection in symptomatic male breast evaluation.
Key Points
- 179 topics and >1,500 clinical scenarios; reviewed every 2 years
- Nine breast imaging topics, including male breast evaluation
- Goal: safe, effective, evidence-aligned imaging utilization
Imaging Modalities for the Male Breast
Diagnostic modalities mirror those used in women: digital mammography (with or without tomosynthesis), ultrasound, and selectively MRI. Nuclear techniques (e.g., MBI/BSGI, PEM) are available in some practices but are not first-line.
Key Points
- Modality selection is driven by age, clinical suspicion, and ACR variants
- Mammography is preferred for men ≥25 years; ultrasound for men <25 years
- MRI is not an initial test; reserved for staging/extent in known cancer
Digital Mammography and Tomosynthesis in Men
Mammography offers high sensitivity/specificity for men ≥25 years, enabling confident diagnosis of gynecomastia and recognition of benign and malignant features. Pectoralis displacement can optimize tissue visualization. Tomosynthesis offers theoretical benefits (margin analysis, lesion conspicuity) though male-specific data are limited.
Key Points
- First-line imaging for indeterminate/suspicious findings in men ≥25 years
- Enables characterization of gynecomastia subtypes (nodular, dendritic, diffuse)
- Technique tip: displace breast off the pectoralis (implant-displaced analog)
- Tomosynthesis may reduce recalls and improve margin assessment
Ultrasound of the Male Breast
Ultrasound is readily available, cost-effective, and first-line in men <25 years. It is best for distinguishing cystic from solid lesions but requires caution: gynecomastia can mimic malignancy sonographically.
Key Points
- Primary modality in men <25; adjunct to mammography otherwise
- Any cystic or solid lesion in men warrants heightened suspicion
- Color Doppler adds no management-changing value
- Targeted scanning of palpable areas and comparative contralateral evaluation are useful
Breast MRI (and Other Advanced Modalities)
Breast MRI is not indicated for initial evaluation per ACR but can delineate extent of disease in newly diagnosed male breast cancer, including skin, nipple–areolar complex, and pectoralis/chest wall involvement, impacting surgical planning. No evidence supports high-risk screening MRI in men with pathogenic variants.
Key Points
- Use for staging/extent after cancer diagnosis; not for screening or initial triage
- MRI can demonstrate muscle invasion vs chest wall invasion, guiding neoadjuvant therapy
- No current data to support high-risk screening MRI in BRCA-positive men
Gynecomastia: Pathophysiology, Clinical Features, and Imaging Types
Gynecomastia reflects proliferation of stromal and ductal elements due to estrogen-androgen imbalance. Clinically, it presents as tender, mobile subareolar tissue and is often unilateral or asymmetric. Most cases require no imaging when exam is classic.
Key Points
- Classic exam: soft, freely mobile subareolar tissue; often tender
- Unilateral and asymmetric presentations are common
- No imaging required when clinical exam is characteristic
- Three imaging types:
- Nodular: round/oval subareolar mass; early/reversible stage
- Dendritic: classic flame-shaped subareolar tissue extending posteriorly; irreversible
- Diffuse: global glandular proliferation resembling a heterogeneously dense female breast
Causes of Gynecomastia (Physiologic, Endocrine, Medications, Systemic Disease)
Gynecomastia arises in predictable physiologic windows and from diverse pathologies and exposures.
Key Points
- Physiologic peaks: neonatal, pubertal, and >60 years
- Endocrine/genetic: hypogonadism, Klinefelter syndrome
- Neoplasia: testicular tumors (e.g., hCG-secreting choriocarcinoma) may present with gynecomastia—mandate thorough physical exam including testicular exam
- Systemic disease: cirrhosis/ESLD, chronic renal failure/dialysis; hepatocellular carcinoma associations
- Medications/substances: diuretics, steroids, marijuana, exogenous estrogens (e.g., gender-affirming therapy)
- Obesity: peripheral aromatization increases estrogen
Pseudogynecomastia
Pseudogynecomastia denotes adipose proliferation without glandular tissue. Clinically indistinguishable from gynecomastia; diagnosis is imaging-based.
Key Points
- Imaging shows fatty tissue without glandular elements
- Managed conservatively; no oncologic implication per se
Other Benign Male Breast Entities
Beyond gynecomastia, benign lesions encountered include fat necrosis, lipoma, sebaceous cyst, mastitis/abscess, fibroadenoma, radial scar, and skin calcifications.
Key Points
- Lipoma: fat-containing, oval, circumscribed mass on mammography/ultrasound; may be intramuscular
- Sebaceous (epidermal inclusion) cyst: subcutaneous lesion with tract to skin (punctum); avoid aspiration/biopsy to prevent inflammatory reaction; surgical excision if needed
- Mastitis/abscess: complex masses with skin/trabecular thickening; aspiration is diagnostic and therapeutic with culture for targeted antibiotics
- Fat necrosis: variable echogenic complex mass; correlate with clinical history (trauma/inflammation)
- Fibroadenoma: rare in men; complex or suspicious features merit biopsy and often excision
- Radial scar/complex sclerosing lesion: warrants surgical excision due to ~12% upgrade risk
- Skin calcifications: “rim calcifications” (BI-RADS 5th ed; formerly “lucent-centered”) are benign; most other grouped microcalcifications in men are suspicious
Malignant Lesions in Men
Invasive ductal carcinoma (IDC) is the most common; DCIS, papillary carcinoma, lymphoma, and metastases (notably melanoma) also occur. Typical primary cancer presents as a hard, fixed, eccentric (non-subareolar) mass, often with nipple/skin changes or discharge.
Key Points
- Imaging: eccentric masses near, but not centered under, the nipple; any mass/calcifications/asymmetry is suspicious
- DCIS can present with microcalcifications alone; biopsy is warranted
- Papillary carcinoma and rare subtypes (e.g., sebaceous IDC) occur
- Primary breast lymphoma is exceedingly rare; consider in systemic disease (e.g., ESLD) with complex mass
- Metastases (melanoma) can present as discrete masses; correlate with oncologic history
- Doppler flow does not alter need for biopsy in suspicious masses
- Bilateral male breast cancer is extraordinarily rare but documented
Risk Factors for Male Breast Cancer
Risk stratification mirrors female risk with male-specific considerations.
Key Points
- Age >60 is the strongest risk factor
- Family history and pathogenic variants (BRCA1/2)
- Exogenous estrogen/progesterone exposure (e.g., long-term gender-affirming therapy >5–10 years)
- Obesity due to aromatization
- Prior chest irradiation (e.g., mantle fields for lymphoma)
Diagnostic Algorithms per ACR Variants
ACR variants tailor imaging to age and clinical suspicion.
Key Points
- Variant 1 (any age, classic gynecomastia on exam): no imaging
- Variant 2 (<25 years, indeterminate exam): ultrasound first; if biopsy considered, obtain limited mammography to identify benign entities (e.g., gynecomastia/fat necrosis) and potentially avert biopsy
- Variant 3 (≥25 years, indeterminate mass): bilateral mammography first; targeted ultrasound as adjunct and for biopsy guidance
- Variant 4 (≥25 years, indeterminate or suspicious on mammography): add ultrasound for characterization and intervention planning
- Variant 5 (any age, suspicious clinical exam—fixed mass, nipple discharge/changes, axillary adenopathy): mammography plus ultrasound; proceed to biopsy for suspicious findings
Interpretation Pearls and Pitfalls in Male Breast Imaging
Approach male breast imaging with heightened suspicion while leveraging pattern recognition and clinical context.
Key Points
- Gynecomastia’s dendritic pattern can mimic invasive cancer on ultrasound but is characteristic on mammography
- In men, any cystic lesion or circumscribed mass is not assumed benign
- Masses, asymmetries, and microcalcifications are suspicious unless unequivocally benign (e.g., rim calcifications)
- Technique optimization (pectoralis displacement) improves mammographic assessment
- Always correlate with physical findings and contralateral comparisons
Incidental Breast Findings on CT
Incidental male breast findings on CT are not definitive and require dedicated breast imaging for characterization.
Key Points
- CT can suggest gynecomastia; otherwise, refer for mammography ± ultrasound
- Do not manage non-characteristic masses on CT without targeted breast imaging
Follow-up and Survivorship in Male Breast Cancer
Post-treatment surveillance parallels female protocols for a defined period.
Key Points
- Annual mammography for 10 years after diagnosis; thereafter, clinical exams if disease-free
- Imaging surveillance of the contralateral breast is prudent during the first decade
Imaging Care for Transgender Women
Transgender women on gender-affirming hormone therapy develop glandular tissue that mirrors diffuse gynecomastia or a heterogeneously dense female breast. Imaging principles align with cisgender female protocols.
Key Points
- Consider screening beginning at age ~50 or 5–10 years after starting estrogen therapy; actual adherence may be variable
- Perform full and implant-displaced CC/MLO views in patients with implants
- Manage palpable masses with a low threshold for biopsy; benign-appearing parallel, circumscribed masses may still warrant tissue diagnosis
- Expect progressive glandular proliferation with longer-term hormone exposure
Conclusion
Evaluation of the male breast hinges on careful clinical assessment, appropriate application of ACR Appropriateness Criteria, and modality-specific strengths. Mammography is the cornerstone for men aged ≥25 years, while ultrasound leads for those <25 years and complements mammography across ages. Gynecomastia dominates presentations and is often diagnosable clinically or with characteristic mammographic patterns. Given the rarity but seriousness of male breast cancer—and the atypically late presentation—maintaining a high index of suspicion for masses, asymmetries, and calcifications is essential. MRI remains a staging tool rather than an entry test, and transgender women should be imaged using female protocols with attention to duration of hormone exposure.
