What are the different types of breast cancer found on biopsy?

From the Guidelines

Breast cancer types identified on biopsy include invasive carcinoma of the breast, not otherwise specified (NOS, previously named ductal carcinoma), which accounts for 70%–75% of all breast cancers, and lobular carcinoma, which accounts for 12%–15% of all breast cancers, as well as 18 other rare subtypes, each with specific morphological traits and prognoses 1. The most common types of breast cancer found on biopsy are invasive ductal carcinoma and invasive lobular carcinoma.

• Invasive ductal carcinoma (IDC) is the most common type, accounting for about 70-75% of all breast cancers, and is also known as invasive carcinoma of the breast, not otherwise specified (NOS) 1.
• Invasive lobular carcinoma (ILC) is the second most common type, accounting for about 12-15% of all breast cancers 1. Other less common types of breast cancer include:
• Ductal carcinoma in situ (DCIS), a non-invasive or pre-invasive breast cancer confined to the milk ducts
• Inflammatory breast cancer, characterized by redness and swelling
• Paget's disease, affecting the nipple
• Medullary, mucinous, and tubular carcinomas, which are typically less aggressive
• Triple-negative breast cancer, which lacks receptors for estrogen, progesterone, and HER2 protein Molecular subtypes based on receptor status include Luminal A, Luminal B, HER2-positive, and Basal-like (often triple-negative) 1. The specific type of breast cancer identified on biopsy is crucial for determining treatment approaches, as different types respond differently to therapies like hormone therapy, targeted treatments, chemotherapy, radiation, or surgery 1. The pathology report from a biopsy also provides information on cancer grade, which indicates how abnormal the cells appear and how quickly they might grow, as well as the presence or absence of certain biomarkers such as estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 (HER2) 1.

From the Research

Types of Breast Cancer

The different types of breast cancer found on biopsy include:

• Ductal carcinoma in situ (DCIS) 2
• Invasive ductal carcinoma (IDC) 3, 4
• Invasive lobular carcinoma (ILC) 3, 5
• Special-type breast cancers, which are categorized into at least 17 discrete pathological entities, including:
  • Tubular carcinoma 3
  • Mucinous A and B carcinomas 3
  • Neuroendocrine carcinoma 3
  • Apocrine carcinoma 3
  • IDC with osteoclastic giant cells 3
  • Micropapillary carcinoma 3
  • Adenoid cystic carcinoma 3
  • Metaplastic carcinoma 3
  • Medullary carcinoma 3

Classification and Diagnosis

Breast cancers can be classified into molecular subtypes, including luminal, basal-like, and HER2+ 3, 4. The diagnosis of breast cancer is typically established by biopsy and histological examination 2.

Subtypes and Prognosis

Some special types of breast cancer, such as medullary and adenoid cystic carcinomas, are associated with a good prognosis, but may display a poor prognosis basal-like transcriptome 3. Invasive lobular carcinoma is typically luminal in molecular subtype and has a characteristic discohesive growth pattern 5.

Biopsy and Excision

Excisional biopsy is often required after a breast core biopsy yields lobular neoplasia, as the upgrade rate to malignancy can be significant 6. The type of malignancy on excisional biopsy pathology can include DCIS, IDC, or ILC 6.