The significance of eccentric foci of hyperpigmentation ('small dark dots') within melanocytic nevi. Analysis of 59 cases.
Fifty-nine melanocytic nevi with eccentric foci of hyperpigmentation ("small dark dots") that measured primarily 1 to 2 mm in diameter were prospectively examined to determine the histologic correlates of the dark dots. Forty-one (69%) of the dark dots were due to increased melanin in epidermal melanocytes and/or keratinocytes, usually accompanied by melanophages; of these 41, six (15%) were associated with slight or moderate melanocytic nuclear atypia. Fifteen (25%) of the dark dots were due to increased dermal pigment that was either superficial or deep. Three (5%) of the dark dots were due to melanoma arising within a nevus. A small percentage of "small dark dots" within melanocytic nevi are due to melanoma. Biopsy specimens of nevi with small dark dots should be sectioned to ensure histologic examination of this focus of hyperpigmentation.