What is Invasive Ductal Carcinoma?
Invasive ductal carcinoma (IDC), also known as infiltrating ductal carcinoma, is the most common type of
breast cancer, accounting for about 80% of all breast cancer diagnoses. IDC begins in the milk ducts and then invades the surrounding breast tissue. Over time, it can spread to the lymph nodes and other parts of the body.
Histological Features
Under the microscope, IDC is characterized by its invasion into the surrounding
stroma and the presence of
malignant epithelial cells. These cells often form irregular glandular structures and can show significant nuclear atypia and mitotic activity. The tumor cells in IDC typically lose the normal
ductal architecture and invade through the basement membrane.
Diagnosis and Staging
The diagnosis of IDC is primarily based on
histopathological examination of a biopsy sample. Key diagnostic features include the absence of a myoepithelial layer, stromal invasion, and the presence of
desmoplastic reaction. IDC is staged based on the size of the tumor, lymph node involvement, and distant metastasis, commonly referred to as the
TNM staging system.
Molecular Subtypes
IDC can be further classified into molecular subtypes based on the expression of
hormone receptors (estrogen and progesterone receptors) and HER2 status. These subtypes include Luminal A, Luminal B, HER2-enriched, and triple-negative. Each subtype has distinct biological behavior and therapeutic responses.
Treatment Options
Treatment for IDC typically involves a combination of
surgery,
radiation therapy, and
systemic treatments such as chemotherapy, hormone therapy, and targeted therapy. The treatment plan is tailored based on the stage of the cancer, molecular subtype, and patient factors.
Prognosis
The prognosis of IDC varies widely depending on the stage at diagnosis, molecular subtype, and response to treatment. Early-stage IDC has a relatively good prognosis with high
survival rates, while advanced-stage disease may have a poorer outlook. Ongoing research and advancements in personalized medicine continue to improve outcomes for patients with IDC.
Histological Grading
IDC is histologically graded using the
Nottingham grading system, which evaluates tubule formation, nuclear pleomorphism, and mitotic count. The grade provides information about the aggressiveness of the tumor and helps guide treatment decisions.
Role of Immunohistochemistry
Immunohistochemistry (IHC) plays a crucial role in the diagnosis and classification of IDC. IHC is used to detect the presence of hormone receptors, HER2 protein overexpression, and other biomarkers that have prognostic and therapeutic implications.
Importance of Early Detection
Early detection of IDC through
screening mammography and other imaging modalities can significantly improve the chances of successful treatment and survival. Regular breast self-examinations and awareness of breast changes are also important for early diagnosis.
