Definition

LCIS is a non-invasive proliferation of abnormal epithelial cells within the lobules of the breast. Despite the term “carcinoma,” it is not considered a true cancer or direct precursor lesion, but rather a marker of increased bilateral breast cancer risk.

Key Points for Oncology Pharmacists

• Nature: Confined to lobules and terminal ducts; does not breach the basement membrane.
• Risk: Increases lifetime risk of developing invasive breast cancer in either breast (about 8–10× higher than the general population).
• Symptoms: Usually asymptomatic; detected incidentally on biopsy.
• Management Role:
  • No chemotherapy is indicated for LCIS itself.
  • Risk-reduction strategies may include selective estrogen receptor modulators (SERMs) such as tamoxifen or raloxifene, or aromatase inhibitors in postmenopausal women.
  • Pharmacist considerations: counsel on benefits vs. risks of chemoprevention (e.g., VTE risk with SERMs, bone health with aromatase inhibitors).
• Surveillance: Enhanced screening—annual mammography ± MRI. Pharmacist may support adherence and educate on imaging schedule.