Since 1890, when acanthosis nigricans was first described independently by Pollitzer1 and by Janovsky,2 about 300 cases have been reported. In no instance heretofore, however, has it been described in association with and immediately overlying deep metastatic malignant growths of the skin. This is different from the associated tumors, which will be mentioned later. The cause of acanthosis nigricans is unknown. In 1895 Darier,3 reporting his third case of the disease, associated with gastric carcinoma, advanced the hypothesis that the cutaneous change was the result of the effect of the malignant growth on the abdominal sympathetic nerves. This mechaniconervous theory was supported by Pollitzer,4 even in regard to the benign, or juvenile form; in this type he speculated that there was some congenital abnormality, such as a fibrous band or benign tumor, interfering up to a certain point with the sympathetic function. In the various case