Both procedures are similar and involve removing a small amount of tissues or cells using a needle. The sample is then sent to Pathology for interpretation by a medical specialist known as a Pathologist. A Fine Needle Aspiration (FNA) involves inserting a thin needle into the tissue that requires sampling and then applying suction to the needle tip whilst turning it. This removes cells that are then analysed. The advantage of an FNA is that it is slightly less invasive than a biopsy, however as the cell samples are small it is possible that the specimen obtained is not sufficient for a confident diagnosis to be made. The procedure may then need to be repeated or “upgraded” to a biopsy.

A biopsy involves the use of a larger needle, which removes a solid block of tissue known as a “core” and is therefore slightly more invasive, though usually feels no different from an FNA as adequate local anaesthetic is used in both procedures. Since a core of solid tissue is removed (unlike the FNA where cells are withdrawn), the specimen is typically sufficient so that a confident and definitive diagnosis can be made.