Pancreas cancer and precancerous cysts can be difficult to diagnose. Sometimes biopsies do not show cancer when cancer is actually present. We hypothesize that genetic differences exist in tissue that is malignant compared to nonmalignant. When patients present with a pancreas mass or cyst, we biopsy it by fine-needle aspiration during upper endoscopy with ultrasound guidance. We would like to use tissue obtained via endoscopic ultrasound guided fine needle aspiration to perform DNA microarray analysis, and compare the differences in gene expression level in the benign tissue compared to cancerous tissue in order to improve our diagnostic capabilities. DNA microarray measures gene expression level rather than germline mutations. The true diagnosis will be based on cytology, surgical pathology, or clinical followup. The performance of the microarray test as a diagnostic test will be compared to the performance of cytology.