Primary malignant melanomas (MMs) of the mucosal membranes have attracted growing attention because of their poor prognosis and the evidence that MM genesis is complicated and involves more factors than UV radiation.The Swedish National Cancer Registry for the years 1960-2004 cited 46402 patients with a primary cutaneous MM, versus 4432 with an extracutaneous MM.However, this numerical difference between cutaneous and extracutaneous MMs in absolute numbers is deceptive.The spatial density (numbers per square unit) of areas that extracutaneous MMs occupy exceeds the average density of that for cutaneous MMs and is even comparable to the density of chronically sun-exposed facial skin! We are conducting systematic epidemiological, clinical, pathological, molecular genetic, virologic, therapeutic, and prognostic studies of archive materials from patients with MMs cited above.The mucosal MMs were often amelanotic and misinterpreted as polyps.