Understanding Invasive Ductal Carcinoma

A breast cancer diagnosis can feel overwhelming. Breast cancer encompasses several distinct types and subtypes, each with unique treatment approaches and outlooks. Learning about your specific subtype empowers you to better understand your diagnosis and make informed decisions with your care team.

What is invasive ductal carcinoma?

Most breast cancers are invasive, meaning cancer cells have spread beyond their point of origin into surrounding breast tissue. Invasive ductal carcinoma (IDC)—also called infiltrating ductal carcinoma—is the most common type of breast cancer, accounting for roughly 80 percent of all breast cancer diagnoses.¹

IDC originates in the cells lining the milk ducts. Over time, cancer cells break through the duct wall and grow into neighboring tissue. At this stage, cancer cells can potentially spread to other body areas through the bloodstream and lymphatic system, a process known as metastasis..¹

Subtypes of invasive ductal carcinoma

IDC includes several distinct histological subtypes. Pathologists also classify IDC by its hormone receptor status (whether tumor cells have receptors for estrogen or progesterone), which plays a key role in dictating treatment strategy.

Less common histological subtypes include:²

• Medullary ductal carcinoma: This rare form often feels spongy rather than like a firm lump and typically shows up on a screening mammogram.
• Mucinous ductal carcinoma: In mucinous ductal carcinoma, cancer cells produce mucus, which combines with the cells to form a tumor.
• Papillary carcinoma: Under a microscope, these cancer cells display small, finger-like projections called papillae. This subtype primarily occurs in women over 60.
• Tubular ductal carcinoma: Named for the tube-like structure of its cells under microscopic evaluation, this is a very rare, slow-growing subtype.

Symptoms and diagnosis of IDC

In its early stages, IDC often causes no noticeable symptoms. Doctors frequently detect early abnormalities during a routine screening mammogram, prompting further testing. In other cases, a person may discover a lump during a self-exam.

Potential signs and symptoms of IDC include:³

• Swelling in all or part of the breast
• Skin irritation, dimpling, or puckering
• Breast or nipple pain
• Nipple inversion (turning inward)
• A lump or swelling in the underarm area
• Unusual nipple discharge
• Redness, scaliness, or thickening of the nipple or breast skin

Doctors diagnose IDC using a combination of clinical evaluations and diagnostic testing. Diagnosis typically involves:⁴

• Physical examination of the breast and underarm (axillary) lymph nodes
• Screening or diagnostic mammogram
• Breast ultrasound
• Breast MRI
• Biopsy (removing a tissue sample to confirm diagnosis and determine the tumor's hormone receptor status)

How is IDC treated?

Treatment for IDC varies based on the stage, histological subtype, and hormone receptor status of the tumor. In many cases, a combination of therapies is used.

Treatment options include:²

• Surgical interventions: Lumpectomy, mastectomy, sentinel node biopsy, axillary node dissection, and breast reconstruction
• Radiation therapy: Targeted high-energy rays that eliminate remaining cancer cells
• Systemic therapies: Chemotherapy, hormonal therapy drugs (for tumors with positive hormone receptor status), and targeted biologic therapies

Your oncology team will customize a treatment plan based on your specific diagnostic profile and discuss the potential risks and benefits of each option.

What is the outlook?

Ongoing research continuously advances breast cancer treatments and improves patient outcomes. Your care team can discuss personalized treatment plans, overall prognosis, and clinical trial opportunities tailored to your specific diagnosis.