- If you are part of the expansion group and have a certain mutation, you will have a biopsy for PD testing. The tumor biopsy will be collected using either a fine needle aspiration or a core biopsy, depending on the location and size of the tumor. To perform a core biopsy, a sample of tissue is removed using a hollow core needle that has a cutting edge. To collect a fine needle aspirate, a small amount of tissue is withdrawn through a needle. If you have questions about your mutation status, the doctor can discuss this with you.