Alpha-foetoprotein heterogeneity: what is its value in managing patients with germ cell tumours?

Alpha-foetoprotein (AFP) is widely used in the diagnosis, therapeutic monitoring and follow-up of patients with germ cell tumours. On occasion, the interpretation of a raised serum AFP measurement in a patient is confounded by the fact that AFP also increases in a variety of liver and gastrointestinal diseases. AFP exists as a number of isoforms, which can be separated by their differential binding to plant lectins. Thus, AFP-concanavalin A (ConA) binding affords a means of distinguishing between a raised AFP of teratoma or liver aetiology and has recently been reported to possess sensitivity and specificity approaching 100%. We present a patient in whom column chromatographic ConA binding was used as a basis for clinical management decisions for treatment for relapsed germ cell testicular tumour. The presumption of high test specificity led to a delay in the diagnosis of cancer recurrence, from which the patient ultimately died. We conclude that the clinical utility of lectin binding assays currently remains uncertain and further evaluation is warranted.