Paraneoplasias of the Skin

Four processes characterize a malignant neoplasm (Fig. 1). 1 Autonomous local cell growth; the tumor cell becomes “correlation deaf”, owing to loss of inhibitory regulators. 2 Tumor cell spread; penetration and metastases, the main indication of malignancy, caused by a large amount of enzyme activity, prostaglandins, etc. 3 Pathologic products of metabolism that lead to the production of hormone-type communication. 4 Host defence mechanisms that come into being mainly by immunologic processes (immune response). This means that a great variety of biochemical, immunologic and other reactions can be shown in every malignant process.