Significance of micrometastases in prostate cancer

Pelvic lymph node metastases have been considered the most potent factor associated with disease recurrence in patients undergoing radical prostatectomy for localized prostate cancer. Routine pathological examination, however, can miss micrometastatic tumor foci in the lymph nodes of patients with prostate cancer, resulting in confused tumor staging and clinical decision-making. Accordingly, intensive efforts have been made to develop a procedure for efficaciously detecting micrometastases in pelvic lymph nodes using several kinds of molecular and histopathological techniques targeting genes specifically expressed in the prostate, such as prostate-specific antigen and prostate-specific membrane antigen. Although some of these techniques have been shown to achieve significantly higher sensitivity for detecting micrometastatic prostate cancer cells in surgically removed pelvic nodes during radical prostatectomy than conventional pathological examination, there have not been any methods introduced into clinical practice. In this review, we attempted to summarize recent advances in the field of "micrometastases" in prostate cancer in order to clarify the clinical significance of micrometastases in patients undergoing radical prostatectomy and to suggest limitations to be overcome before developing a reliable model for clinical application.