Seborrheic keratoses are very common. They are benign growths with a characteristic brown, waxy appearance. They are mostly hereditary and are not related to sun exposure. They tend to increase in number the older one gets, although there are younger patients who have considerable numbers of them. Conventional wisdom has always held that there is no need to biopsy seborrheic keratoses, because they are uniformly benign. In my practice, I have found notable exceptions to this rule. In several instances, I have discovered melanomas growing inside a seborrheic keratosis, and they were found only because biopsy was elected. Because of the danger that melanoma poses, I recommend that seborrheic keratoses be biopsied as a matter of course.