Breast cyst: Clinical sciences

Breast cysts are fluid filled masses that develop within the glandular tissue of the breast, usually in the upper outer quadrant; but they can appear anywhere in the breast. Overall, breast cysts are the most common cause of breast symptoms, and they typically arise in patients assigned female at birth between the ages of 35 and 50 years, usually because of an overproduction of estrogen and suppression of progesterone. Fortunately, most breast cysts are benign; but new cysts in older postmenopausal patients pose a higher risk of underlying malignancy, and this risk increases if they are currently on hormone replacement therapy.

Alright, now, when a patient presents with a chief concern suggesting a breast cyst, the first step is to obtain a focused history and perform a physical examination. The most commonly reported symptom is a breast lump and possibly localized pain that worsens just prior to menstruation each month. However, some patients can be asymptomatic, and a breast lump can be discovered as part of a physical examination performed for another reason.

Speaking of which, physical examination findings that suggest a breast cyst include a palpable, solitary, smooth and firm breast mass that is freely mobile. Occasionally, the mass can also be tender on palpation. With these findings, you can suspect a breast cyst.

The next step is to order a breast ultrasound to confirm your diagnosis. If there are no findings on the ultrasound that would indicate a breast cyst, then you should consider an alternative diagnosis. On the other hand, if a breast cyst is identified, ultrasound findings can help classify it as either a simple, complicated or a complex cyst.

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. BI-RADS is typically used for mammography findings, but it can be applied for ultrasound as well. So, with BI-RADS, 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 imaging 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 take a look at some ultrasound findings that suggest the presence of a simple breast cyst. The ultrasound might show an oval or round lesion that is well-circumscribed with posterior acoustic enhancement but without any internal echoes or solid components. The lesion can also have visible thin walls and septa that are less than 0.5 mm thick. If just these findings are present, you are dealing with a simple breast cyst, which is classified as BI-RADS 2, or benign. Of note, there’s no increased risk of breast cancer detected in a mass that fulfills the ultrasound diagnostic criteria of a simple cyst.

Alright, let’s talk about treatment. If your patient is asymptomatic, no intervention is necessary, and you can simply continue with routine breast cancer screening. On the other hand, if your patient experiences symptoms like pain and discomfort, then the next step is an ultrasound-guided aspiration. If there is a complete collapse of the cyst after aspiration, no further interventions are needed, so you can continue with routine breast cancer screening. However, if the cyst doesn’t collapse completely or there is blood in the aspirate, your next step is to perform an ultrasound-guided core needle biopsy.