Ductal Carcinoma In Situ — Non-Invasive Breast Cancer

Ductal carcinoma in situ represents the earliest form of breast neoplasia. In this condition, epithelial cells lining the milk ducts undergo neoplastic transformation, multiplying abnormally. However, they remain strictly confined by the basement membrane of the duct, meaning they have not acquired the capacity to invade the adjacent stroma, blood vessels, or lymphatic channels.

Historically detected only when forming a palpable breast lump, DCIS is now predominantly identified through routine population-based screening mammography. While DCIS itself is not life-threatening because it cannot metastasise in its contained state, untreated lesions carry a risk of progressing to invasive ductal carcinoma over time.

A diagnosis of DCIS allows for treatment before any invasive cancer has developed, offering an exceptionally high cure rate. Understanding that DCIS is non-invasive helps patients navigate decisions without immediate panic, distinguishing it from invasive forms of breast cancer. Care choices, such as selecting between breast-conserving surgery or mastectomy, depend on lesion size, location, and grade. Because individual lesions vary in their likelihood of becoming invasive, discussions with a multidisciplinary clinical team ensure that treatment protects against future cancer risks while avoiding unnecessary surgical or systemic overtreatment.

DCIS is typically detected on a screening mammogram as suspicious clusters of microcalcifications, usually without any palpable lump. Diagnosis is confirmed through a core needle biopsy guided by mammography or ultrasound. The tissue is evaluated for tumour grade and tested for oestrogen receptor and progesterone receptor expression using immunohistochemistry.

Ductal carcinoma in situ relates exclusively to breast cancer. It specifically involves the epithelial lining of the mammary ducts. While DCIS is confined to the breast, it shares biological characteristics with invasive ductal carcinoma, which is the most common form of invasive breast cancer diagnosed worldwide.

Management generally involves surgical removal via breast-conserving surgery (lumpectomy) or mastectomy, ensuring clear margins. If lumpectomy is chosen, adjuvant radiotherapy is frequently recommended to reduce local recurrence. For hormone receptor-positive DCIS, endocrine therapy, such as tamoxifen or an aromatase inhibitor, may be offered. Chemotherapy is not indicated because DCIS does not spread systemically.