The characteristics of disseminated tumor cells in pancreatic cancer: A black box needs to be explored

Despite recent advances in early diagnosis and surgical treatment, the clinical outcome of patients with pancreatic cancer has not been improved markedly. One of the reasons for the dismal outcome is early dissemination of tumor cells. Sensitive immunohistocytochemical and nucleic acid-based assays have detected disseminated tumor cells in the lymph nodes, bone marrow, peritoneal cavity or peripheral blood. Formation of the metastatic disease depends on the nature of the disseminated tumor cells. Standardization of protocols is mandatory to detect occult tumor cells in clinical practice. We present an overview of recent studies on the incidence, prognostic values and some characteristics of occult tumor cells disseminated in the secondary sites of patients with pancreatic cancer.