A lymph node metastatic cell line (UP-LN1) was established in vitro from a poorly-differentiated epithelial tumor, and characterized for immunobiological and molecular cytogenetic profiles. The morphology of UP-LN1 cells when grown as monolayers was unique in that, apart from typical colonies of adherent epithelial cells, many loosely attached round cell colonies emerged on and around the patches of epithelial cells. By means of immunofluorescence/flow cytometric analysis, UP-LN1 cells showed selective expression of cytokeratin markers AE1 and CK20, but expressed AE3 and CK7 poorly. The expression of CEA and CK20 but not CK7 in UP-LN1 cells was also exhibited in the tumor biopsy by immunohistochemistry, suggesting a gastrointestinal origin of this tumor. Down-regulation of HLA-class I and other surface molecules including ICAM-1, CD44s, CD44v5, CD44v6 and E-cadherin were observed, which all pointed to a progressive/invasive phenotype of the tumor. Spectral karyotyping revealed a hypertriploid (approximately 3n) chromosome content with 73-76 chromosomes, including numerical alterations and translocated derivative chromosomes. Seven different translocation chromosomes were observed, four of which involved chromosome 19. Numerical imbalances were also assessed by comparative genomic hybridization. This cell line should be useful for further studies of tumor invasion and metastatic processes because of the unusual in vitro and in vivo immunobiological and genetic characteristics observed.