The biopsy is typically requested when imaging tests such as ultrasound, CT scan, or MRI have revealed a suspicious mass or lesion that requires further evaluation. It may also be used to monitor the progression of cancer or to evaluate the effectiveness of treatment. During the procedure, a needle is inserted through the skin and into the mass or lesion using ultrasound guidance, and a small tissue sample is collected for examination. The procedure is typically performed on an outpatient basis and can take about 30-60 minutes to complete.