A dermatoscope is a handheld device with a 10 × lens, light-emitting diode (LED) lighting, and polarizing filters that allow for visualization of skin structures in the epidermis and papillary dermis such as melanin and blood vessels. It is most commonly used to diagnose melanocytic lesions (eg, benign nevi, atypical nevi, and melanoma) (Figures 18-5 and 18-6), basal and squamous cell carcinomas, and benign tumors (eg, angiomas, seborrheic keratoses, and sebaceous gland hyperplasia).9 The first step in dermoscopy of tumors is distinguishing melanocytic tumors from nonmelanocytic tumors and the second step involves reaching a specific diagnosis using various algorithms.10,11 The 3-point algorithm for melanocytic tumors is discussed on page 165 in Chapter 18. Studies have shown that even a 1-day training course in dermoscopy improves primary care clinicians' detection of skin cancers.12 Training courses are regularly offered by organizations such as the International Dermoscopy Society and the American Academy of Dermatology.
Dermoscopy is also useful in the diagnosis of several other cutaneous disorders including scabies, lice, hair and scalp disorders, and several inflammatory disorders (eg, psoriasis and lichen planus).13 It also can be used to detect nail fold capillary abnormalities in connective tissue diseases.14