Malignant melanoma and adenocarcinoma of a Barrett oesophagus.

An adenocarcinoma with a malignant melanoma in a Barrett oesophagus is extremely rare. We did not find any other cases in the English literature. The diagnosis of a malignant melanoma can be difficult but can be made by tissue examination with a special immunoreaction with several markers to see it expresses S-100, but lacks activity for KER and EMA. S-100 is relatively non-specific as a single immunodeterminant in the diagnostic separation of melanoma and anaplastic carcinoma, but very sensitive. Immunohistochemically, these tumours react to S-100 protein, neuron-specific enolase and HMB-45 antibody (less sensitive than S-100), but not to cytokeratin or CEA. In our case it was obvious that there were two different tumours because the MM was negative for cytokeratin, but the adenocarcinoma was positive for cytokeratin.