noun
Medical term for a pigmented spot on the skin, including both lentigo (flat) and mole (raised). In everyday language, ほくろ is more common.
皮膚科で黒子の検査を受けた。
I had a mole examined at the dermatology clinic.
この黒子は良性のものです。
This lentigo is benign.
Sino-Japanese compound of 黒 (black) and 子 (small thing/child), referring to a small dark spot on the skin. The reading こくし is the on'yomi of the characters.