The black esophagus (BE) is endoscopically seen as diffuse, circumferential, black
lesion usually in distal one –third of esophagus and extension to proximal esophagus
is common.
http://medcraveonline.com/MOJCR/MOJCR-07-00207.pdf
Black Esophagus due to Metastasis Colonic Carcinoma