Foci of stromal melanocytes (so-called blue naevus) of the uterine cervix in Japanese women.

Foci of stromal melanocytes (FSM) of the uterine cervix have been known as extra-cutaneous "blue naevus". However macroscopic and histological findings suggest that FSM of the cervix are analogous to dermal melanocytosis, rather than to cutaneous blue naevus and the lesions are more appropriately called stromal melanocytosis. FSM of the cervix have been considered rare, but our study showed that they are not uncommon in Japanese women occurring in 8.6% (42/486). The lesions were initially observed in the third decade of life and became most prevalent in the fifth decade (15/86 cases, 17.4%). In stroma of the cervix, stromal melanocytes (SM) were present where many peripheral nerve fibres were seen. SM of the cervix were positive for S-100 protein in immunohistochemical studies and were sometimes observed close to peripheral nerve fibres. Melanocytes were never observed in the ectocervical and endocervical epithelium, but only in the stroma of the cervix. We suggest that malignant melanoma of the uterine cervix may originate from SM.