Mesothelioma Diagnosis & Tests - Biopsy While imaging tests can detect abnormalities, they don’t always identify exactly what the abnormalities are. For this reason, the findings of an X-ray, CT scan or both often lead to a pathological evaluation done via needle or surgical biopsy. With a biopsy, a tissue sample taken from the body will be reviewed under a microscope to determine if the tumor is benign (non-cancerous) or malignant (cancerous). The tissue will often be "stained" to determine the type of cancer and examined to determine the types of cells involved (epithelial, sarcomatoid, or mixed/biphasic). A biopsy is performed under local anesthesia. In some cases, sedation/analgesia may be needed. To prepare for the procedure, the patient must typically stop eating 6 hours before the biopsy, and they must abstain from smoking for 48 hours before the procedure. To begin, the patient will change into a hospital gown and an IV (intravenous line) will be pla...