Disseminated isolated tumor cells in bone marrow of esophageal cancer cases

In this study, we reviewed reports on the clinical significance of isolated tumor cells (ITC) in the bone marrow of patients with esophageal cancer and other solid tumor malignancies. We examined studies on bone marrow as a target organ for ITC identification and also looked at the appropriate sites and most efficient methodologies for bone marrow extraction to evaluate the presence of ITC. A diverse number of different cells exist in bone marrow, and it is important to distinguish disseminated cancer cells from other cell types, such as progenitor cells and endothelial cells. Among the various types of cells found in the bone marrow, we confirmed the presence of disseminated cells that can proliferate under specific cell culture conditions. Finally, we discuss recent studies related to the clinical significance of ITC in bone marrow that are associated with prognosis or recurrence in cases of solid cancers, including esophageal cancer. We concluded that the clinical significance of bone marrow as the target organ for identification of ITC varies among different types of cancer and that further study is required to determine a bona fide marker for predicting prognosis or recurrence in cases of esophageal cancer. © 2007 Japan Esophageal Society and Springer-Verlag.