Changes in glycosylation of glycoproteins and glycolipids is a common feature of cancer and may influence cancer cell behaviour, perhaps by enabling cell-cell interactions which favour metastasis or by allowing cancer cells to evade immuno-surveillance. Studies to identify glycosylation changes in human cancer have often used immunohistochemical techniques with lectins or antibodies and human tissue sections. Whilst some detailed biochemical studies have been performed there are few clinically relevant studies since the numbers of specimens evaluated are often very small. Using an immuno-histochemical approach, we have found that the lectin HPA from the albumen gland of Helix pomatia detects aggressive metastatic breast cancers. We have sought to identify the breast cancer associated oligosaccharides and the proteins to which they are attached via 2-DE for proteome analysis and HPLC separations for glycosylation mapping. Sixty-nine breast cancer specimens were studied. The HPA staining pattern, clinical treatment and follow-up data were known. Oligosaccharides that related to HPA staining were identified and found in elevated levels in metastatic breast cancer specimens. Human breast and colorectal cancer cells grown in vitro and in a clinically relevant animal model of metastasis also show increased levels of the oligosaccharides. We are now structurally characterising the oligosaccharides and aim to use them as diagnostic tools and targets for immuno-therapy of breast and other solid tumours.