The CD44 molecule and CD44 isoforms are expressed on some malignant tumours and it has been suggested that their expression may correlate with tumour spread. Human pancreatic carcinoma cell line (HPC-4) expressing CD44 was established from a patient with adenocarcinoma of pancreas. This line showed a rapid growth in vitro, several chromosome abnormalities and surface expression of some adhesion molecules (ICAM-1, LFA-3, beta 1-chain of VLA integrins, VNR). Xenotransplanted HPC-4 cells were able to grow rapidly in SCID mice as subcutaneous tumour, leading to 100% mortality within 3-5 weeks when 1 x 10(5)-1 x 10(7) cells were inoculated. Spontaneous metastases in the liver, lung, spleen and kidney of SCID mice were observed. Interestingly enough, HPC-4 cells in vivo and ex vivo also expressed HLA-DR molecules, but these were rapidly lost upon culture in vitro. It is suggested that the appearance of HLA-DR may be the result of interaction of the tumour with a local environment of the host, while CD44 expression may explain the rapid growth and occurrence of distant metastases in SCID mice. The ability of HPC-4 cells to form spontaneous metastases in SCID mice may prove to be a potentially interesting model of human carcinoma for testing new treatment modalities.