Ductal carcinoma in situ: Clinical sciences

Ductal carcinoma in situ, or DCIS, previously known as intraductal, noninvasive, or non-infiltrating carcinoma, refers to a neoplastic lesion within the mammary ductal system that hasn’t yet invaded through its basement membrane into the surrounding tissues. If there’s evidence of basement membrane invasion, then the lesion is upstaged to invasive carcinoma.

When assessing a patient with signs and symptoms consistent with DCIS, the first step is to obtain a focused history and physical exam. Sometimes, a patient may present after noticing a breast lump or even nipple discharge. However, the majority of patients will not have historical or physical exam findings, and they’ll be discovered on routine mammogram screening, which shows a lesion that may or may not have microcalcifications.

Be sure to ask about risk factors, such as a personal or family history of breast cancer, prior diagnosis of atypical ductal hyperplasia, early menarche or late menopause, and nulliparity or first birth after the age of 30. Additional risk factors include age greater than 40, a known history of dense breast tissue, and more than five years of hormone replacement therapy. On the flip side, physical exam findings might include a palpable breast mass or changes in the appearance of the nipple or skin. Keep in mind that most patients won’t present with any physical exam findings.

Here’s a clinical pearl! Biologically male patients and those who identify as transgender or non-binary are also at risk for breast cancers, so it’s important to screen them, especially as these populations frequently go underdiagnosed.

Okay, now that we have our history and physical exam, let’s move on to some imaging. The next step is to obtain a diagnostic mammogram. Unlike a screening mammogram, which is used on asymptomatic patients, diagnostic mammograms are performed in patients with evidence of disease, either in the history and physical, or with a prior abnormal screening mammogram, and involves more comprehensive imaging for a more thorough visualization of the breasts than a screening mammogram. If imaging doesn’t reveal any suspicious findings, or if findings are confirmed to be radiographically benign in appearance, then you should continue current screening mammogram recommendations.

Alright, let’s talk about potential findings in our diagnostic mammogram. You may see microcalcifications, which are small deposits of calcium clusters that appear radiopaque on imaging; these are suggestive of pathology in the mammary ductal system, and can indicate the presence of neoplastic changes. There are certain shapes and patterns of microcalcifications that can indicate DCIS, and in order of increasing suspicion, these patterns include coarse heterogeneous, amorphous, fine pleomorphic, and fine linear or fine branching calcifications. Other imaging findings can include a soft tissue mass, or an area of architectural distortion. Although none of these image findings are pathognomonic for DCIS, they should raise your suspicion for malignancy.

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.

Okay, after imaging, the next step is to get a core needle biopsy for pathology, which may help us confirm DCIS.

Here’s a clinical pearl! Core needle biopsy is the standard way to obtain breast tissue for histology, and surgical excisional biopsy is generally not recommended. However, in rare cases, excisional biopsy is still performed. A couple of examples include a prior non-diagnostic sample from a core needle biopsy, or unsuitable anatomy, like a lesion that’s too close to the skin, too close to the chest wall, or right next to a breast implant. These biopsies can be tricky, as the lesions in DCIS are not always palpable, meaning a radiologist will need to help localize the lesion for the surgeon to excise.