Similarly to the in vivo results of Chen et al., the receptor positive HT1080 tumours were visualised with high contrast in comparison with the background; however, the APN/CD13 negative MCF-7 tumours showed only slight tracer accumulation in the bilateral tumour-bearing female athymic nude mice (HT1080 and MCF-7) [31,55]. The gene discussed is ANPEP; the disease is neoplasm.