Purpose: To characterize and classify malignant conjunctival melanomas with exclusively corneal invasive growth.
Design: Population-based, nationwide retrospective cross-sectional study.
Participants: Patients with primary malignant conjunctival melanoma diagnosed between 1967 and 2000 in Finland.
Methods: On the basis of all available clinical and histopathologic data of tumors diagnosed during the study period, malignant conjunctival melanomas that first demonstrated invasive growth on the cornea without evidence of conjunctival tumors other than primary acquired melanosis were identified, their prevalence calculated, and their characteristics reviewed. On the basis of these cases and literature data, a classification for "corneal melanoma" was developed.
Main outcome measures: Frequency and type of corneal involvement, recurrence, and survival.
Results: Patients with exclusively corneal invasive tumor accounted for 5% (95% confidence interval, 1-12) of 85 consecutive primary conjunctival melanomas. Two were separated from the limbus by clear cornea (type I), and two paralleled but did not invade the limbal conjunctiva (type II). Two were associated with clear evidence of primary acquired melanosis. None of the tumors recurred after local excision, and no metastases were observed during a median follow-up of 2 years 5 months (range, 1 year 8 months-7 years 10 months).
Conclusions: Primary malignant conjunctival melanomas can grow on the cornea without conjunctival involvement other than acquired melanosis. They are easily removed and do not cause lymphatic metastases. The term "corneally displaced malignant conjunctival melanoma" would best describe their supposed conjunctival origin and actual corneal location.