What is ductal carcinoma?

What is Ductal Carcinoma?

Ductal carcinoma refers to a malignant proliferation of epithelial cells originating within the breast ducts, which exists in two distinct forms: ductal carcinoma in situ (DCIS), where cancer cells remain confined within the ductal basement membrane without invasion, and invasive ductal carcinoma (IDC), where cancer cells have breached the basement membrane and invaded surrounding breast tissue. 1, 2

Ductal Carcinoma In Situ (DCIS)

Core Definition

• DCIS represents a heterogeneous group of neoplastic lesions in the breast ducts that have not invaded beyond the ductal basement membrane 3, 1
• It is considered a non-obligate precursor of invasive breast cancer, meaning not all DCIS will progress to invasion 4, 5
• If left untreated, approximately 20-40% of DCIS cases will evolve into invasive cancer, though the exact proportion and timeline remain uncertain 6, 7, 5

Clinical Significance

• DCIS has an excellent prognosis with 10-year overall survival rates of 97.2% to 98.6% when appropriately detected and treated 1
• Before mammography screening, DCIS accounted for only 2-3% of breast cancers; it now represents approximately 20-27% of all newly diagnosed breast cancers in the United States 1, 8
• The dramatic increase in DCIS diagnosis is primarily due to widespread screening mammography detecting clinically occult disease 1, 6

Presentation Characteristics

• The most common presentation is mammographically detected microcalcifications (90-98% of cases) 3, 1
• These calcifications are typically pleomorphic (varying in size, form, and density), often arranged in linear or segmental patterns reflecting their ductal distribution 3
• Approximately 10% of DCIS presents without calcifications, sometimes as a mass or other soft tissue changes 3
• Definitive diagnosis requires pathologic evaluation, as imaging alone cannot determine whether basement membrane invasion has occurred 1

Invasive Ductal Carcinoma (IDC)

Core Definition

• IDC represents 70-75% of all invasive breast cancers and occurs when malignant cells have breached the ductal basement membrane 9
• Unlike DCIS, IDC has the potential to metastasize to lymph nodes and distant sites 2

Prognosis Determinants

• Prognosis varies significantly based on tumor grade, with higher grade tumors having worse outcomes 9
• Axillary lymph node status remains one of the strongest prognostic indicators 9
• Special histologic subtypes (mucinous, tubular, adenoid cystic) have particularly favorable prognoses compared to standard IDC 2, 9

Critical Clinical Distinction

The fundamental difference between DCIS and IDC is the presence or absence of invasion through the basement membrane—this single pathologic feature determines whether the disease has metastatic potential and dramatically influences treatment approach and prognosis. 1, 5

Common Pitfall

• Underestimating occult invasive disease: approximately 25.9% of cases diagnosed as DCIS on core-needle biopsy are upstaged to invasive cancer at surgical excision 1, 2
• This upstaging rate emphasizes why definitive surgical pathology is essential for accurate diagnosis and treatment planning 1