Purpose: To evaluate the clinical features and risks for transformation of conjunctival primary acquired melanosis (PAM) into melanoma.
Design: Noncomparative case series.
Participants: Three hundred eleven eyes with conjunctival PAM without melanoma at initial examination from a single-center tertiary referral center.
Methods: Retrospective chart review with evaluation of the clinical features of PAM at initial presentation and follow-up. Times to PAM enlargement, recurrence, and transformation into melanoma were assessed using Kaplan-Meier estimates. Risk factors for these outcomes were analyzed using Cox proportional hazards regressions.
Main outcome measures: Primary acquired melanosis enlargement, recurrence, and transformation into melanoma.
Results: Mean patient age at diagnosis of PAM was 56 years (range, 15-90), 62% were female, and 96% were Caucasian. The conjunctival quadrant(s) affected by PAM were temporal (57%), inferior (45%), nasal (42%), and superior (37%). The anatomic location(s) of PAM included bulbar conjunctiva (91%), limbal conjunctiva (55%), cornea (23%), forniceal conjunctiva (13%), palpebral conjunctiva (12%), and caruncle (11%). Primary acquired melanosis extended for a mean of 3 clock hours (range, 1-12). Initial management included observation (n = 194 eyes [62%]), biopsy combined with cryotherapy (n = 107 eyes [34%]), and topical chemotherapy and/or cryotherapy without biopsy (n = 10 [4%]). Of PAM that was observed, Kaplan-Meier estimates at 10 years revealed PAM enlargement in 35% and transformation into melanoma in 12%. Of those that underwent incisional or excisional biopsy, 10-year estimates of PAM recurrence and transformation into melanoma were 58% and 11%, respectively. Progression to melanoma occurred in 0% of cases of PAM without atypia, 0% of cases of PAM with mild atypia, and 13% of cases of PAM with severe atypia. Of the 9 patients with PAM who developed melanoma, none have developed systemic metastasis. Multivariable analysis revealed that the most significant factor for both PAM recurrence and progression to melanoma was extent of PAM in clock hours.
Conclusion: Primary acquired melanosis without atypia or with mild atypia shows 0% progression to melanoma, whereas PAM with severe atypia shows progression to melanoma in 13%. The greater the extent of PAM in clock hours, the greater the risk for transformation to melanoma.