Biological relevance of occult tumor cells in a lymph node of a patient with resectable esophageal cancer

Background: The presence of immunohistochemically detectable isolated tumor cells in lymph nodes of patients with carcinoma of the gastrointestinal tr act correlates with poor prognosis. However, the biological relevance of th ese cells is still unclear. Further analyses of such occult tumor cells are limited because of their extremely low frequency. Methods: Tissue samples from a lymph node classified as positive by immunoh istochemistry but negative by routine histopathology and the autologous pri mary tumor wc:re harvested for cell culture and two permant cell lines coul d be generated. Both cell lines were analysed using microsatellite analysis , HLA-DRB1*genotyping, FAGS, M-FISH and SCID mice xenograftassay. Results: In FAGS and M-FISH analysis, both cell lines showed overexpression of p53 and p185(erbB2), were in a hypertriploid range and showed loss of t he Y chromosome. Furthermore, both cell lines displayed tumorigenic behavio ur in vivo after transplantation into SCID mice. Re-establishment of tumor cell lines from different murine organs indicates the presence of micrometa stases in these organs. Conclusion: These data provide first direct evidence that immunohistochemic ally identifiable tumor cells in lymph nodes are viable malignant tumor cel ls, which implies that these cells might be precursors of subsequent metast atic lesions.