A Halsted mastectomy is a surgical procedure used to treat breast cancer. It involves the removal of the entire breast, including the underlying chest muscle and surrounding lymph nodes. This approach aims to eliminate cancerous tissue and reduce the risk of recurrence. Developed by surgeon William Stewart Halsted in the late 19th century, this technique was one of the first radical treatments for breast cancer. While it was once a standard procedure, advancements in medical techniques and understanding of breast cancer have led to less invasive options being preferred in many cases today.