BackgroundSerial tissue expansion is performed to remove giant congenital melanocytic nevi. However, there have been no studies comparing the expansion rate between the subsequent and preceding expansions. In this study, we analyzed the rate of expansion in accordance with the number of surgeries, expander location, expander size, and sex.MethodsA retrospective analysis was performed in pediatric patients who underwent tissue expansion for giant congenital melanocytic nevi. We tested four factors that may influence the expansion rate: The number of surgeries, expander location, expander size, and sex. The rate of expansion was calculated by dividing the ‘inflation amount’ by the ‘expander size’.ResultsThe expansion rate, compared with the first-time group, was 1.25 times higher in the second-or-more group (P=0.04) and 1.84 times higher in the third-or-more group (P<0.01). The expansion rate was higher at the trunk than at other sites (P<0.01). There was a tendency of lower expansion rate for larger expanders (P=0.03). Sex did not affect the expansion rate.ConclusionsThere was a positive correlation between the number of surgeries and the expansion rate, a positive correlation between the expander location and the expansion rate, and a negative correlation between the expander size and the expansion rate.

It is known that the ecchymosis occurs due to the leakage of red blood cells through the blood vessels. However, few materials and methods are known for its treatment. Prostaglandin E1 expands the blood vessel and is widely used in plastic and reconstructive surgeries. We made ecchymosis on the legs of the rats, and used prostaglandin E1 as a candidate for the treatment material of ecchymosis. In this study, the ecchymosis area after 3, 4 days was significantly smaller in the experimental group than the control group. This tendency continues until the 9 days. The results of this study show that prostaglandin E1 is effective for the resolution of ecchymosis.