What is a biopsy used for in medical practice?

A biopsy is a medical procedure in which a small sample of living tissue is removed from the body for microscopic examination. This is crucial for diagnosing various conditions, particularly cancer, as it allows healthcare professionals to evaluate the tissue structure and cellular characteristics. The microscopic analysis can reveal the presence of abnormal cells and help determine the nature of the disease, its stage, and potential treatments.

When a biopsy is performed, it is typically done to clarify a diagnosis when other tests may not be definitive. The information gleaned from the biopsy can be essential for guiding treatment decisions. The term "living tissue" indicates that the sample is taken from a part of the body where cellular activity is occurring, which is a key feature distinguishing a biopsy from other types of tissue removal or testing.

While the other options involve various medical procedures or assessments, they do not accurately define the specific purpose and method of a biopsy as well as "the excision of a small piece of living tissue for microscopic examination" does.