Borderline and atypical melanocytic lesions.

The importance of correct diagnosis of melanocytic lesions cannot be overemphasized. Prognosis and treatment of these patients are based on the pathological diagnosis. The superficial melanocytic lesions are difficult to diagnose and pose frequent diagnostic dilemmas. Benign, dysplastic, and early malignant melanocytic tumors can be diagnosed based on more or less characteristic features. The pattern of growth, cytology of the melanocytes, and the lymphocytic, and stromal reaction are the histological cornerstones for diagnosis. Another diagnostic problem is the so called "borderline" melanocytic neoplasm. These lesions are characterized by a distinctive nodular growth phase. The difficulty in distinguishing some of these neoplasms from atypical fibroxanthoma is emphasized.