Skin changes may accompany or precede internal malignancy. Some associations reflect immune changes in the patient as a response to the neoplasm, and others have a common origin in the neoplastic process. The significance of the association varies from no more than chance up to a valuable help in diagnosis of the pathology. The nature and site of the most likely neoplasm can often be suggested, and sometimes the prognosis can also be forecast.
Newbold PCH. Skin Markers of Malignancy. Arch Dermatol. 1970;102(6):680-692. doi:10.1001/archderm.1970.04000120098020