High prevalence of angiotropism in congenital melanocytic nevi: an analysis of 53 cases.

The mechanisms responsible for the development of congenital melanocytic nevi (CMN) have yet to be elucidated. A potential clue to their origin is the observation of angiotropism of nevus cells in CMN. Interestingly, neural crest stem cells (NCSCs), the precursors of melanocytes, demonstrate angiotropism in the embryo. There is accumulating evidence that NCSCs migrate along the external surfaces of vessels during a portion of their journey to the skin. Comparable angiotropism and migration of melanoma cells have been described as extravascular migratory metastasis in melanoma. In this report, we systematically examined for the first time, the frequency of angiotropism in 53 CMN. The lesions originated from 27 females and 26 males with an average age of 9.81 years (range 0.42-28 years). The mean nevus size was 7.43 cm (range 0.3-40 cm). Twenty-seven (50.9%) of the 53 lesions were less than 1.5 cm in diameter. Sixteen nevi (30.2%) were medium sized (1.5-19.9 cm), and 10 CMN (18.9%) were large/giant (>20 cm in diameter). The trunk was the most common location (23/53) followed by the head and neck (17/53). Thirty-eight (71.7%) of the 53 lesions were compound melanocytic nevi, and 15 (28.3%) of the 53 lesions were dermal nevi. In summary, angiotropism was observed in 50 (94.3%) of 53 cases. Consequently, such angiotropism may potentially explain the origin of the precursor cells giving rise to CMN. Further explanations concerning dysregulated growth are clearly needed for the actual appearance of CMN and their physical characteristics.