Lecture Notes: Subtypes of Breast Cancer

Overview

• Breast cancer is common but not homogenous.
• It is categorized into different subtypes:
  • Biological subtypes: Based on the cell of origin.
  • Clinical subtypes: Based on treatment methodology and molecular features.

Biological Subtypes

• Ductal Carcinoma

  • Most common subtype.
  • Originates from the milk ducts.
  • Cancer of the epithelial layer of tissues.
  • Characterized by a palpable or imageable tumor.

• Lobular Carcinoma

  • Originates from the milk glands (lobules).
  • Considered a rare subtype.

• Inflammatory Breast Cancer

  • Rare (2-5% of cases).
  • No identifiable primary tumor.
  • Characterized by rapid spread and inflammation of the whole breast.

Clinical Subtypes

• Defined by the molecular biology or treatment methods rather than cell origin.

• Estrogen Receptor-Positive (ER-Positive):

  • About 70% of breast cancers.
  • Expresses estrogen and/or progesterone receptors.
  • Most survivable due to targeted therapies.

• HER2 Positive:

  • About 15% of breast cancers.
  • Overexpression of HER2 receptor, not normal.
  • Growth factor receptor causing aggressive cell growth.
  • Targeted by specific drugs.

• Triple Negative:

  • No expression of estrogen receptor, progesterone receptor, or HER2 overexpression.
  • Most challenging to treat due to lack of specific targets.
  • Greatest mortality rates in breast cancer.

Conclusion

• Biological subtypes focus on the origin cell type, while clinical subtypes focus on treatment options.
• Understanding these subtypes is crucial for effective treatment and management of breast cancer.