ABSTRACT
First step In the first step the dermoscopist needs to classify the lesion under investigation as melanocytic or non-melanocytic. This classification is based on certain structures that, when present, help to correctly classify the lesion as melanocytic (see Chapter 1 for definitions and examples of network, pseudonetwork, globules, streaks, homogeneous blue pigmentation and parallel pattern), basal cell carcinoma (BCC), hemangioma, seborrheic keratosis or dermatofibroma. If the lesion does not have any positive criteria for a melanocytic lesion and also lacks any positive criteria for a nonmelanocytic lesion then the lesion needs to be considered, by default, to be of melanocytic origin (Figure 2.2). These so-called featureless melanocytic lesions need to be viewed with caution, since melanoma can present in this manner, especially in the presence, within the lesion, of irregular vessels and dotted vessels (see Chapter 3b on vascular structures).
