Disease Description (Causes and Symptoms)
- Definition and pathophysiology: Carcinoma in situ of the breast is a noninvasive breast cancer (stage 0) in which cancer cells are confined to the epithelium of the breast ducts or lobules and have not invaded the basement membrane. Representative types include ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS). DCIS is considered a precursor lesion of invasive breast cancer, whereas LCIS is often regarded as a marker of increased future breast cancer risk (particularly bilateral risk).
- Causes (risk factors): Estrogen exposure (early menarche/late menopause, hormone replacement therapy), radiation exposure, family history and genetic mutations (such as BRCA), alcohol consumption, obesity (especially after menopause), smoking, and a high-fat diet.
- Main symptoms: Most cases are asymptomatic and are discovered incidentally on mammography (microcalcifications). Some patients may have nipple discharge, a localized lump, or changes in the nipple skin.
Treatment Methods
- Confirming the diagnosis: After imaging (mammography, breast ultrasound, and MRI when necessary), a biopsy (core needle biopsy or Mammotome/vacuum-assisted biopsy) is performed for histological confirmation and testing of hormone receptors (ER/PR) and HER2.
- Local treatment
- Breast-conserving surgery (wide local excision; breast-conserving surgery/partial mastectomy) + radiation therapy: Generally considered standard to reduce the local recurrence rate (especially for DCIS).
- Mastectomy (total mastectomy): Selected for multifocal lesions, extensive lesions, high risk of recurrence, or according to patient preference.
- Sentinel lymph node biopsy: Generally not necessary for pure DCIS, but sentinel lymph node biopsy may be considered when mastectomy is performed or invasion is suspected.
- Systemic treatment (adjuvant therapy)
- For hormone receptor-positive DCIS, tamoxifen (usually for 5 years) may be recommended to reduce the risk of recurrence and breast cancer in either breast. An aromatase inhibitor may be considered in postmenopausal patients in some cases (individualized).
- Standard antibody therapy (such as trastuzumab) for HER2-positive DCIS is generally not recommended, although investigational approaches may be available.
- Watchful waiting (surveillance): Clinical trials evaluating active surveillance for some cases of low-risk DCIS are ongoing, but the current standard is surgical treatment.
- Lifestyle management and precautions: Avoid alcohol, manage weight (especially after menopause), exercise regularly, and discuss the risks when using hormone replacement therapy. If you are planning a pregnancy, discuss the timing and method of treatment with your treating medical team.
Checklist Before an Outpatient Visit (Including Recommended Items and Sample Questions)
- Recommended items to bring
- A list of medications currently being taken (including hormonal medications) and a history of allergies
- Previous breast-related test results (mammography, ultrasound, MRI) or copies of the reports
- Notes summarizing your family history (including breast cancer and ovarian cancer)
- A record of when symptoms began and how they have changed (nipple discharge, changes in size, etc.)
- Sample questions useful during an outpatient visit (things patients may ask their healthcare providers)
- What do the results of my recent tests mean?
- Is my lesion DCIS or LCIS, and what do the biopsy findings (hormone receptors and HER2) show?
- Do I need any additional tests or genetic testing (for example, BRCA testing)?
General Sample Questions to Ask the Doctor
- What is the risk of recurrence of this lesion or progression to invasive cancer?
- Is surveillance instead of surgery an option in my case? What are the advantages and disadvantages of surveillance?
- Will I need radiation therapy or medication (such as tamoxifen) after surgery (breast-conserving surgery versus mastectomy)? What are the side effects?
Disease-Specific Sample Questions
- (1) Do my biopsy results show DCIS or LCIS, and what are the results of the ER/PR/HER2 tests? How will this affect the choice of treatment?
- (2) If I choose breast-conserving surgery instead of wide local excision, how likely is it that I will need radiation therapy or additional excision? Also, do I need a sentinel lymph node biopsy?
Additional guidance: The choice of treatment varies depending on the pathological findings of the lesion (pathological subtype, extent, and suspicion of microinvasion), imaging findings, and the patient's age, preferences, and family history. Please consult with your breast surgeon and radiation oncologist to establish a detailed treatment plan. In addition, it is recommended to follow regular screening according to the recommendations of the Korean Breast Cancer Society (for example, breast self-examination after age 30, clinical examination after age 35, and regular mammography after age 40).