[Nevus of Ota. Presentation of a case associated with a cellular blue nevus with suspected malignant degeneration and review of the literature].

BACKGROUND

Nevus of Ota is a melanotic pigmentary disorder ("dermal melanocytosis"), mostly congenital or acquired, involving the skin innervated by the first and the second branch of the trigeminal nerve, hence its descriptive label of "nevus fuscus coerulaeus ophthalmic and maxillaris". In more than half of patients this condition is associated with "ocular melanocytosis" ("melanosis oculi") involving the conjunctiva, the sclera, the uveal tract and possibly the optic nerve. In some cases a condition of "orbital melanocytosis" with involvement of orbital fat and periosteum by dendritic melanocytes is on record as well as in some other patients an analogous condition of "leptomeningeal melanocytosis" is present. At histology tissues from the above sites are seen infiltrated by dendritic melanocytes which can vary in number from so scarce up to so numerous that a diagnosis of a blue nevus of the common type is warranted. Sometimes the finding of a variously pigmented typical cellular blue nevus in the skin and alternatively that of heavily pigmented melanocytoma in the eye ("nevus magnocellularis") or in the meninges (so-called "melanotic meningioma") are respectively observed.

MATERIALS AND METHODS

A case of cellular blue nevus with histologically uncertain malignant potential in a nevus of Ota of 30 years duration in a white female patient aged 59 is described. The lesion which was surgically totally removed grossly appeared nodular shaped and 2 cm sized. Histologically it consisted of a fairly well-circumscribed proliferation of melanocytic spindle-shaped cells growing in a vaguely fascicular pattern. On the basis of random nuclear atypicalities and pleomorphism and additionally by virtue of the presence of a few scattered mitoses (one of which was atypical) but in absence of frank necrosis a diagnosis of unpredictable biologic behaviour seemed to be warranted. The patient was closely followed-up but no adjunctive therapy given. Four years after the excision and diagnosis no local recurrence or distant metastasis has been discovered. A computerized search of previously recorded cases of melanomas in nevus of Ota was made.

CONCLUSIONS

Forty-eight cases of malignant melanomas complicating this clinico-pathological setting are on record, mostly in the uveal tract, followed by locations in central nervous system, skin, and retro-orbital fatty tissue. Melanomas arising in nevus of Ota tend to be low grade lesions that do infiltrate locally but rarely metastasize. The importance of a closely dermatological and ophthalmic surveillance of patients with nevus of Ota is emphasized.