[Extracutaneous malignant melanomas: clinical aspects and biology]

Approximately 5% of all malignant melanomas originate from primarily non-cutaneous sites. They are preferentially distributed along the choroid, the meninges, the subserous space of the oesophagus and the intestinal tract, at transitional areas of mucous membranes, and along organ capsules, the periadventitial tissues of major blood vessels, and, occasionally, muscle fasciae. Little is known about their biological behaviour; the prognosis, however, generally has to be considered less favourable than that of primary cutaneous malignant melanomas, probably at least in part because they are often not discovered until they are in advanced stages. There are no specific clinical signs suggestive for non-cutaneous malignant melanomas; symptoms vary with the site of manifestation of the tumours. Interpretation of these clinical data based on results from comparative anatomical studies leads to the conclusion that extracutaneous malignant melanomas in humans are residuals of phylogenetically old, extensive and well-developed non-cutaneous pigment cell patterns demonstrable in a variety of lower vertebrates, which result from interactions between organogenesis and pigment cell development during ontogeny. This demonstrates that consideration of fundamental principles of developmental biology can give diagnostic clues to the localizations at which primary non-cutaneous malignant melanomas may be suspected and can thus facilitate decisions about what diagnostic procedures are necessary.