Breast Imaging — Comprehensive Differential Diagnoses
Complex Solid and Cystic Mass
Benign
- Fibrocystic changes
- Intraductal or intracystic papilloma without atypia
- Fibroadenoma
Atypical
- Atypical ductal hyperplasia (ADH)
- Atypical papilloma
- Lobular neoplasia (ALH, LCIS)
Malignant
- DCIS
- IDC
- ILC
Cystic with Solid Elements
- Post-op fluid collection
- Post-traumatic fluid collection
- Papilloma
- Oil cyst/fat necrosis
- Galactocele
- Intracystic papillary carcinoma
- IDC-NOS
Solid with Cystic Features
- Complex fibroadenoma
- PASH
- Fat necrosis
- Necrotic IDC
- Post-op fluid collection
- Papillary carcinoma
- Mucinous carcinoma
- Metastases
Calcification Differential Diagnoses
Amorphous/Smudgy Calcifications
- Milk of calcium: amorphous on CC (layering), “teacup” or linear on lateral
- Sclerosing adenosis
- Flat epithelial atypia (FEA)
- ADH
- Columnar cell change
- Fibroadenoma
- Fat necrosis
- Mucocele-like lesions
- Lobular neoplasia (less likely)
- DCIS (usually lower grade)
Fine Linear Branching — Group or Linear/Segmental Distribution
- DCIS (higher grade) — most important
- Early stage fat necrosis, fibroadenoma, or dystrophic calcs
- Early vascular or secretory calcs
- Suture calcs
- Parasites
- Autoimmune conditions: dermatomyositis, scleroderma, lupus
Architectural Distortion DDx
- Malignant: IDC, ILC, DCIS (rarely)
- Benign/High-risk:
- Complex sclerosing lesion/radial scar
- Stromal fibrosis
- Surgical scar
- Trauma
- Fat necrosis
- Sclerosing adenosis (proliferation of acinar, myoepithelial, connective tissue elements)
- Papilloma (with or without sclerosing features)
- LCIS, FCC, PASH
- Fibromatosis (fibroblastic and myofibroblastic proliferation)
Ultrasound Differential Diagnoses
Hyperechoic Masses on US
(Almost always benign — only ~0.5% malignant)
- Lipomas
- Fat necrosis
- Angiolipomas
- Hemangiomas
- Hematoma
- Galactoceles
- Abscess
”Round” (Circumscribed) Cancers
- IDC-NOS (most common)
- Medullary carcinoma
- Mucinous carcinoma
- Papillary carcinoma
- Phyllodes tumor (malignant)
Lymphadenopathy Differential Diagnoses
Benign Causes of Intramammary and Axillary Lymphadenopathy
| Laterality | Causes |
|---|---|
| Unilateral | Bartonella henselae (cat scratch), other reactive nodes from recent infection on that side (breast, arm, upper back) |
| Bilateral | CVD (RA, scleroderma, lupus), granulomatous disease (sarcoid, TB), HIV, dermatopathic (dermatitis, psoriasis, rashes), silicone adenopathy, fungal (histoplasmosis) |
Calcifications in Lymph Nodes
- Tattoos
- Gold therapy (arthritis treatment)
- Metastases (psammoma bodies: papillary thyroid, ovarian papillary cystadenocarcinoma)
- Granulomatous disease (TB, sarcoid)
MRI-Specific Differential Diagnoses
Focus on MRI
- Lymph node
- Papilloma
- Fibroadenoma
- FCC
- UDH
- ADH
- IDC
- DCIS
Non-Mass Enhancement (NME) on MRI
- FCC (fibrocystic change)
- PASH
- UDH (usual ductal hyperplasia)
- ADH
- ILC
- DCIS
- Linear NME: per-ductal inflammation, FCC, ADH, DCIS
BI-RADS 5 Mimics
Findings that can be mistaken for cancer (BI-RADS 5 appearance but benign):
- Common benign mimics:
- Chronic and inflammatory mastitis
- Granulomatous mastitis
- Fat necrosis
- Complex sclerosing lesion/radial scar
- Granular cell tumor
- Infection
- Less common benign mimics:
- Lymphocytic (diabetic) mastopathy
- Atypical infection
- Fibromatosis or desmoid tumor
- Myofibroblastoma
- Amyloid
Diagnostic Mammo DDx by Finding
Fat-Containing Masses (Always Benign)
- Hamartoma (mixed density)
- Lipoma (all fat)
- Oil cyst (fat with rim)
- Fat necrosis (fat + rim calcs)
- Galactocele (fat/fluid mixture)
- Lymph node (fat hilum)
Multiple Bilateral Well-Circumscribed Masses
- Cysts (most common)
- Fibroadenomas
- Metastases (melanoma, lung, kidney, lymphoma, sarcoma)