Invasive Ductal Carcinoma (IDC)
~Introduction
Invasive Ductal Carcinoma (IDC), also known as Infiltrating Ductal Carcinoma, is the most common type of breast cancer, accounting for nearly 70–80% of all invasive breast malignancies. It arises from the epithelial lining of the milk ducts and, unlike ductal carcinoma in situ (DCIS), invades through the basement membrane into the surrounding breast stroma, allowing the potential to spread to lymph nodes and distant organs.
IDC represents a clinically significant disease because of its variable biological behavior, ranging from slow-growing tumors to highly aggressive cancers.
~Epidemiology
Most common breast cancer worldwide
Predominantly affects women over 40 years
Incidence increases with age
Rare in men (<1% of cases)
Higher prevalence in developed countries due to lifestyle and screening practices
~Etiology and Risk Factors
IDC develops due to a combination of genetic, hormonal, and environmental factors.
Hormonal Factors
Early menarche
Late menopause
Hormone replacement therapy
Nulliparity or late first pregnancy
Genetic Factors
Family history of breast cancer
BRCA1 and BRCA2 mutations
TP53 and PTEN gene mutations
Lifestyle Factors
Obesity (especially postmenopausal)
Alcohol intake
Physical inactivity
Other Risk Factors
Previous radiation exposure to chest
History of DCIS or atypical ductal hyperplasia
Dense breast tissue
~Pathogenesis
IDC usually begins as DCIS, where malignant cells are confined to the ducts. Over time, additional genetic alterations enable tumor cells to break through the basement membrane, invade surrounding connective tissue, and gain access to lymphatic and blood vessels.
Key features of invasion include:
Loss of myoepithelial layer
Degradation of extracellular matrix
Angiogenesis
~Gross Pathology
Irregular, hard mass
Poorly circumscribed
Gray-white cut surface
Often produces a desmoplastic reaction, making the tumor firm
~Histopathology
Microscopic Features
Malignant ductal cells infiltrating stroma
Formation of duct-like structures
Variable pleomorphism
Increased mitotic activity
Tumor Grading (Nottingham System)
Grading is based on:
Tubule formation
Nuclear pleomorphism
Mitotic count
Grades:
Grade I (well differentiated)
Grade II (moderately differentiated)
Grade III (poorly differentiated)
~Molecular Classification
IDC is classified based on receptor status:
Hormone Receptor Positive
Estrogen receptor (ER) positive
Progesterone receptor (PR) positive
HER2-Positive
Overexpression of HER2/neu oncogene
More aggressive but responsive to targeted therapy
Triple-Negative Breast Cancer
ER-, PR-, HER2-
Aggressive behavior
Limited targeted treatment options
~Clinical Features
Symptoms
Painless breast lump
Change in breast size or shape
Skin dimpling (peau d’orange)
Nipple retraction or discharge
Breast pain (late stage)
Signs
Hard, irregular mass
Fixed to skin or chest wall in advanced cases
Axillary lymphadenopathy
~Diagnostic Evaluation
Mammography
Spiculated mass
Architectural distortion
Microcalcifications
Ultrasound
Hypoechoic irregular mass
Posterior acoustic shadowing
MRI
Useful in dense breasts
Assesses extent and multifocal disease
Biopsy
Core needle biopsy is diagnostic
Determines histology and receptor status
~Staging (TNM System)
T – tumor size
N – lymph node involvement
M – distant metastasis
Stages range from Stage I to Stage IV.
Common metastatic sites:
Bone
Lung
Liver
Brain
~Management and Treatment
Treatment depends on stage, receptor status, patient age, and overall health.
Surgical Treatment
Breast-Conserving Surgery
Lumpectomy with clear margins
Followed by radiation therapy
Mastectomy
Indicated for large tumors or multicentric disease
Axillary Evaluation
Sentinel lymph node biopsy
Axillary lymph node dissection if positive
Radiation Therapy
Given after breast-conserving surgery
Reduces local recurrence
Sometimes used post-mastectomy
~Systemic Therapy
Chemotherapy
Used in high-risk or advanced disease
Neoadjuvant or adjuvant setting
Hormonal Therapy
For ER/PR-positive tumors:
Tamoxifen
Aromatase inhibitors
Targeted Therapy
For HER2-positive tumors:
Trastuzumab
Pertuzumab
~Prognosis
Prognosis depends on:
Tumor size
Lymph node status
Histologic grade
Molecular subtype
Survival Rates
Early stage: excellent prognosis
Advanced stage: reduced survival
5-year survival rate overall: ~90% (early stages)
~Complications
Disease-Related
Local recurrence
Distant metastasis
Treatment-Related
Lymphedema
Cardiotoxicity (HER2 therapy)
Chemotherapy side effects
~Prevention and Screening
Primary Prevention
Healthy diet and exercise
Limiting alcohol
Weight control
Secondary Prevention
Regular mammography
Genetic counseling for high-risk individuals
~Recent Advances
Personalized medicine
Genomic profiling
Immunotherapy for triple-negative cancers
De-escalation of therapy in low-risk cases
~Difference Between DCIS and IDC
| Feature | DCIS | IDC |
|---|---|---|
| Invasion | No | Yes |
| Stage | 0 | I–IV |
| Metastasis | Absent | Possible |
| Prognosis | Excellent | Variable |
~Conclusion
Invasive Ductal Carcinoma is the most prevalent and clinically significant form of breast cancer. Early detection through screening, accurate pathological diagnosis, and advances in multimodal therapy have significantly improved survival rates. A personalized, multidisciplinary approach remains the cornerstone of effective management.
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