ほくろの色とかたち—子供と大人でこんなに違う—

抄録

Introduction: We notice a big difference between children and adults. Nevi of the children tend to be flat and black, while those of adults are often elevated and hypopigmented. These differences could be explained by the depth of melanin distribution. The black or brown color is due to epidermal melanin, but blue-gray is because of dermal melanin. General Change of Nevus: The number of nevi would increase during puberty and decrease after the age of 40. The diameter of a nevus would increase up to 3 to 6 mm for the first few years and be stable after that, while the elevation might occur after the puberty or during pregnancy. Histopathological Classification of Nevus: Nevi are histopathologically classified into three categories, namely junctional, compound, and dermal, depending on the depth of melanocytic proliferation. Melanocytes in the junctional nevus mainly situated at the dermo-epidermal junction. Those in the compound type proliferate both at DEJ and the dermis. Those in the dermal nevus exclusively grow in the dermis. The junctional nevi remain to be flat during the life. Nevus on the Face: Facial nevi tend to be flat in the childhood, but become hemispherically elevated after the puberty. Nevus on the Trunk and Extremities: Nevi are flat and globular in the childhood and might transition to papillomatous type (Unna type). Nevi that appeared after the adolescence, are reticular on dermoscopy and remain to be flat and might disappear in the senescence. Nevus on the Palms and Soles: Nevi typically shows parallel furrow pattern on dermoscopy. They become hypopigmented in the senescence. Dynamic Change of Nevus (Spitz Nevus): The spitz nevus could change in the short period. It might be noted globular, followed by starburst, and then become reticular or homogeneous. It even might disappear in a few years.