H&E staining of both tail tumours revealed a biphasic appearance, with pseudoglandular or rosette-like structures alternating with areas of spindle cell growth (Fig 2C) and both the pseudoglandular and spindle cell elements stained positive for the melanoma marker Melan-A (Fig 2D) but negative for two alternative melanoma markers S100 and HMB-45 (Fig 2E and 2F). The gene discussed is MLANA; the disease is melanoma.