A fine needle aspiration is the simplest, least invasive test and uses the smallest needle to simply remove cells from the abnormality. This is not always adequate to obtain a diagnosis, depending on the area to be biopsied.
A core needle biopsy removes not only cells, but also a small amount of the surrounding tissue. This provides additional information to assist in the identification of the lesion.
An incisional biopsy takes out even more surrounding tissue. It takes out some of the abnormality, but not all. The doctor will slice into the lesion and remove only a portion of it. If the lesion is found to be cancerous, further surgery may be needed to remove the whole abnormality.
An excisional biopsy generally removes the entire area in question.