1.1 Introduction Ultrasound has become a unique medical imaging tool in the investigation of dermatological diseases. By providing high- resolution gray scale images and blood flow information in real time, ultrasound can provide detailed anatomic and physiologic data of skin lesions and deeper soft-tissue changes. Lesion size in three dimensions-lengths, width and depth, morphology, inner structure -solid, cystic or mixed, homogeneous or inhomogeneous, foci of calcifications or necrosis, location, and extension can be diagnosed. By defining vascularity in real time, color and spectral Doppler ultrasound have been proven useful in the study of localized lesions of the skin. Interventional procedures such as tumor biopsy, collection drainage, foreign body removement. and needle localization of lesions can safely be performed under ultrasound guidance. The detailed anatomic information pro- vided by sonography is useful in planning surgery. Magnetic resonance imaging (MRI) is frequently recommended for preoperative assessment although it requires the use of intra- venous contrast media and can be less efficient in detecting tumors