We report a novel treatment for giant congenital
melanocytic nevi (GCMN) that involves the reuse of resected
nevus tissue after high hydrostatic pressurization (HHP). However, the remaining
melanin pigments in the inactivated
nevus tissue pose a problem; therefore, we performed a long-term observation of the color change of inactivated
nevus tissue after HHP. Pressurized
nevus specimens (200 MPa group, n = 9) and non-pressurized
nevus tissues (control group, n = 9) were subcutaneously implanted into nude mice (BALB/c-nu) and then harvested 3, 6, and 12 months later. Color changes of the
nevus specimens were evaluated. In the 200 MPa group, the specimen color gradually regressed and turned white, and brightness values were significantly higher in the 200 MPa group than in the control group after 6 months. This indicated that
melanin pigments in the pressurized
nevus tissue had spontaneously degraded and regressed. Therefore, it is not necessary to remove
melanin pigments in HHP-treated
nevus tissue.