Breast neoplasms

Breast neoplasms consist of a wide spectrum of pathologies from benign proliferations, high-risk lesions, precursor lesions, to invasive malignancies.​ This article provides an overview for radiologists, with a focus on breast cancer. For a summary article for medical students and non-radiologists, see breast cancer (summary).

Epidemiology

Breast cancer is the most common nonskin malignancy in women. In the affluent populations of North America, Europe, and Australia, 6% of women develop invasive breast cancer before age 75, compared to a 2% risk in developing regions of Africa and Asia ⁸. The difference has been attributed to risks associated with a Westernized lifestyle, including high-calorie diet rich in fat and protein and physical inactivity ⁸.

Risk factors

• increasing age ⁸
• reproductive lifestyle factors increasing unopposed estrogen load ⁸
  • early menarche
  • nulliparity, infertility, or, if parous, few children with late age at first delivery
  • lack of breastfeeding
  • late menopause
  • unopposed estrogen hormone replacement therapy
• personal history of breast cancer or a high risk breast lesion
• first degree relative with breast cancer
• genetic mutations
  • BRCA1 or BRCA2 mutation
  • Li Fraumeni syndrome
  • Peutz Jegher syndrome
  • Cowden syndrome
  • ataxia telangiectasia
  • MEN1 ¹⁰
• thoracic radiation therapy ⁸
• alcohol consumption ⁸

Pathology

Classification

The main pathological classification of breast neoplasms is published by the World Health Organization: WHO classification of tumors of the breast.

The vast majority of breast cancers are adenocarcinomas (99%). The most common types are ⁸:

• invasive carcinoma of no special type (ductal carcinoma not otherwise specified): 40-75%
• ductal carcinoma in situ: 20-25%
• invasive lobular carcinoma: 5-15%

Categories of benign epithelial neoplasms include: 

• papillary lesions
• adenomatous lesions

Non-epithelial malignancies are uncommon and include:

• breast sarcomas (0.5-3% ⁶)
• malignant phyllodes tumor
• metastases to the breast
• breast lymphoma
• fibromatosis of the breast

Immunophenotype

Three molecular biomarkers are routinely evaluated in invasive breast cancers because they have therapeutic implications:

• estrogen receptor (ER)
• progesterone receptor (PR)
• human epidermal growth factor receptor 2 (HER2; proto-oncogene Neu; receptor tyrosine-protein kinase erbB-2)

Staging

Staging of breast tumors is performed according to the TNM system published by the American Joint Committee on Cancer (AJCC) / Union for International Cancer Control (UICC): breast cancer (staging).

Radiographic appearance

Dedicated evaluation of the breast involves multiple imaging modalities to detect and localize lesions for biopsy. In all modalities, regional metastasis can be suspected by the presence of axillary adenopathy.

Mammography

Neoplasms have varied appearances, including masses, asymmetries, calcifications, or architectural distortions. 

Ultrasound

Neoplasms can appear as masses or architectural distortions. Calcifications can sometimes be seen.

MRI

Neoplasms can manifest as masses with or without enhancement, non-mass enhancement, or foci of enhancement.

CT

Breast masses may be incidentally identified but CT is not the preferred modality for dedicated breast evaluation. If calcifications are visualized on CT, they are nearly all benign ⁹.

Radiology report

The use of a standard lexicon is recommended to enhance communication with referrers and audit performance: breast imaging-reporting and data system (BI-RADS).