Cutaneous manifestations of internal malignancy: diagnosis and management.

An association between systemic malignancy and cutaneous manifestations has long been recognized. The cutaneous features that can occur are numerous and heterogeneous, and many different etiologic mechanisms are represented - from direct tumor invasion of skin or distant metastases to a wide variety of inflammatory dermatoses that may occur as paraneoplastic phenomena. In addition, there are a number of inherited syndromes that carry an increased risk of cutaneous as well as internal malignancies. While some of these inherited syndromes and paraneoplastic phenomena are exceedingly rare, all clinicians will be aware of the common cutaneous manifestations of advanced malignant disease such as generalized xerosis and pruritus. This review classifies these wide-ranging cutaneous manifestations of internal malignancy into five basic groups and provides practical advice regarding diagnosis and screening of patients who initially present with a cutaneous complaint. Also included is up-to-date information on two rapidly expanding and exciting areas of research that are likely to have far-reaching clinical implications: (i) clarification of underlying humoral mechanisms, for example, in the malignant carcinoid syndrome; and (ii) identification of an increasing number of specific genetic defects that confer a susceptibility to malignancy.Increased clinician awareness regarding the associations between these lesions and internal malignancy or inherited syndromes will facilitate screening and early diagnosis.