A patient with breast cancer has a related pericardial effusion. Which of the following is a common metastatic site for breast cancer?

Breast cancer is known to metastasize to several organs, with the liver being one of the most common sites for such metastasis. The process of metastasis in breast cancer typically involves the spreading of cancer cells through the bloodstream or lymphatic system to distant organs. The liver's rich blood supply and its anatomical location make it a frequent target for metastatic breast cancer.

When breast cancer cells enter the bloodstream, they may travel to the liver, where they can establish new tumors, leading to symptoms such as abdominal pain, jaundice, or liver dysfunction. Detecting liver metastases often involves imaging techniques, such as ultrasound or CT scans, and can impact treatment decisions.

In contrast, while kidney, pancreas, and colon can also be affected by metastatic disease, they are not typical primary sites of metastasis for breast cancer. Instead, the liver stands out as a well-documented and significant metastatic site in breast cancer patients, which is why it is identified as the correct answer in this case.