Quadrant distribution of dysplastic nevus syndrome.

A 59-year-old man with numerous aggregated pigmented lesions confined to the left upper quadrant of his body is described. The lesions consist of lentigines, common acquired nevi, and dysplastic nevi. In addition, within this quadrant two malignant melanomas at different stages of progression developed from dysplastic nevi. This patient presents a hitherto undescribed quadrant type of dysplastic nevus syndrome. As quadrant syndromes are due to single mutations, our observation strongly supports the concept of an autosomal-dominant trait in dysplastic nevus syndrome.