Invasive ductal carcinoma: Clinical sciences

Invasive ductal carcinoma is the most common form of breast cancer, and occurs when malignant epithelial cells from ductal tissue infiltrate through their basement membrane. Treatment of invasive breast cancer is based on the stage of cancer. Patients are roughly classified as early-stage, locally advanced, or metastatic disease.

When a patient presents with a new breast lump or abnormal screening mammogram, you should consider an invasive ductal carcinoma. The first step is to obtain a focused history and physical exam. History may include changes in the breast or nipple appearance, nipple discharge, and the presence of swollen lymph nodes.

You should also ask about common risk factors, such as a personal or family history of breast or ovarian cancer; early menarche or late menopause; nulliparity; first birth after 30 years of age; being older than 40; dense breast tissue; chest radiation; exogenous hormone use; and family or personal history of deleterious cancer gene mutations like BRCA.

On the flip side, a physical exam might reveal a palpable breast lump, which could be fixed and is more concerning for malignancy. There may also be skin changes; or nipple changes, like flattening or inversion. Some patients even have lymphadenopathy, which can be above and below the clavicle, and in the axilla.

Your next step will be to obtain some labs, including baseline CBC and CMP. Labs might show elevated transaminases or alkaline phosphatase.

Alright, these findings should prompt you to get imaging with a diagnostic mammogram and an ultrasound.

Here’s a clinical pearl! Breast findings on imaging can be categorized with a standardized system called BI-RADS, which stands for Breast Imaging-Reporting and Data System. The imaging findings are assigned into categories labeled as 0 to 6. First, 0 means incomplete, which needs additional imaging or comparison with previous images if available. Next, 1 is negative, meaning that mammography is normal, with no findings like masses or calcification; while 2 indicates findings are completely benign, meaning that mammography reveals findings with no probability of malignancy; a category of 0, 1, and 2 can only be used when undergoing routine screening.

On the other hand, 3 is probably benign, meaning that mammography may reveal a finding with minimal malignant potential of less than 2%, so these patients should get follow-up imaging. Next, 4 is suspicious for malignancy, meaning that mammography may reveal a finding with malignant potential between 2 to 94%, where biopsy will likely be indicated. Then, a category of 5 is highly suspicious of malignancy, with malignant potential over 95%. Lastly, 6 is known malignancy that has been proven with biopsy, and requires definitive management with surgery, chemotherapy, or radiation.

Now, let’s talk about imaging findings that are suspicious for invasive ductal carcinoma. A diagnostic mammogram might show a spiculated or irregular soft tissue mass. You may also see microcalcifications, which should raise suspicion for an underlying malignancy. On ultrasound, you might see an irregularly shaped soft tissue mass that can be taller than it is wide, with a hypoechoic appearance and posterior acoustic shadowing.

If your imaging does not have these findings, you should consider an alternative diagnosis. However, if imaging has any of these signs, you should suspect invasive ductal carcinoma.

Here’s a clinical pearl! If your initial imaging isn’t concerning, but you still have high suspicion for breast cancer, you can obtain an MRI for better visualization.

Okay, now that we suspect invasive ductal carcinoma, our next step is to get a core needle biopsy.

If the core needle biopsy does not show any malignant cells, you’ll again need to consider an alternative diagnosis. However, if the biopsy shows malignant epithelial cells that arise from ductal tissue, and they invade through the surrounding basement membrane, you can confirm your diagnosis of invasive ductal carcinoma.