To determine the degree of melanoma cell intravasation and circulating melanoma cells as well as pulmonary metastasis, we first analysed the expression of the melanoma-specific gene S100B in peripheral blood (day 14 post tumour inoculation) and lungs from melanoma-bearing animals26 (at endpoint, day 18 post tumour inoculation). The gene discussed is S100B; the disease is neoplasm.