Sometimes your doctor feels it is necessary to obtain a small portion of tissue (a biopsy) from an area of concern to determine the nature of a problem. This tissue is sent to the pathology laboratory, processed and examined by a pathologist (a specialist physician) who determines if the tissue is a cancer or some other process that gives your doctor the information needed to properly treat you.
There are times an area of concern is deep within the body and not easily accessible. At these times, your doctor may request the FNA (Fine Needle Aspiration) biopsy be performed. Tissue is obtained by using a very small gauge needle inserted into the area of concern, usually by CT scan or ultrasound guidance (in order to accurately sample the correct area). Tissue is obtained and sent to the pathology laboratory for proper processing and examination.
Additionally, during some surgeries, a surgeon may need to send some tissue to pathology for a frozen section (cutting a thin portion of tissue to place on a glass slide) to determine a diagnosis to guide the remainder of the surgical procedure for the most appropriate treatment.