[494] Angiotropism in Congenital Melanocytic Nevi: Clinicopathological Study of 56 Cases.

Victor B Kokta, Rola Al Dhaybi, Raymond L Barnhill. CHU Sainte-Justine, Montreal, QC, Canada; Universite de Paris Diderot, France

Background: Angiotropism has been reported anecdotally in congenital melanocytic nevi (CMN). Barnhill et al recently described medium-sized CMN demonstrating angiotropism of melanocytes about blood vessels (type non specified), and suggested that extravascular migration may be an important mechanism in the development of CMN. This study evaluates the presence or absence and type of angiotropism according to the size of CMN (giant, intermediate or small) in a pediatric tertiary care hospital between 2007 and 2009.
Design: We reviewed the charts of the CMN and only those in which the surface diameter was specified were included in this study: 25 small CMN (less than 1.5cm diameter), 20 intermediate CMN (between 1.5 and 20cm diameter)and 11 giant CMN (greater than 20cm diameter). The histopathology slides of these CMN were evaluated to assess the depth of CMN, the presence or absence of angiotropism, as well as the type of involved vessels in case of angiotropism. D2-40 was performed in all cases.
Results: Regardless of vessel-type, overall melanocytic angiotropism was observed in 36% in small CMN, 75% of intermediate CMN, and 100% of giant CMN. Refer to table 1 for a comparative view of specific vessel-type melanocytic angiotropism according to congenital nevus size.

Table 1: Specific vessel-type melanocytic angiotropism according to CMN size

CMN - size	lymphatic %	capillary %	venule/arteriole %
small, n=25	36	0	0
intermediate, n=22	70	20	5
giant, n=11	64	36	55

Conclusions: Our study showed that melanocyte angiotropism is a frequent finding in CMN. This frequency increases with the size of CMN; 36% in small CMN, 75% of intermediate CMN, and 100% of giant CMN. Moreover, the angiotropism involves lymphatics in small CMN, whereas capillaries, venules and arterioles are almost exclusively involved in intermediate and giant CMN. Melanocytic angiotropism is found in cutaneous venules and arterioles in 55% of giant CMN! These findings demonstrate the increased chance of angiotropism with the increased diameter size of CMN, support the theory of Barnhill et al suggesting that extravascular migration of neural crest stem cells may be an important mechanism for the development of CMN.
Category: Dermatopathology

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 121, Tuesday Morning