1. To assess the value of serum α-l-fucosidase (EC 18.104.22.168) as a marker for hepatocellular carcinoma, the activity was measured in patients with hepatocellular carcinoma and in control subjects.
2. Mean serum α-l-fucosidase activity was significantly greater in 35 patients with hepatocellular carcinoma (225 ± 69 nkat/l) than in 35 patients with cirrhosis and 20 normal subjects (134 ± 30 and 93 ± 28 nkat/l, respectively). The overlap between hepatocellular carcinoma and cirrhosis, however, was such as to severely limit any value of the enzyme as a diagnostic test.
3. In four cirrhotic patients with hepatocellular carcinoma, an increased enzyme activity was detectable in samples taken up to 66 months before the tumours were diagnosed clinically.
4. The serum activity of α-l-fucosidase fell to within the reference range after liver transplantation for hepatocellular carcinoma in three patients and in one of these a subsequent rise was associated with tumour recurrence which was diagnosed at 8 months after the rise in activity. Ineffective cytotoxic chemotherapy was also associated with a progressive rise in serum α-l-fucosidase activity.
5. α-l-fucosidase activity in tumour tissue was significantly lower than that seen in non-tumour tissue from cirrhotic patients. These reductions may represent increased transport from the tissue and may partly account for the increased serum activity found in some patients with hepatocellular carcinoma.