Primary acquired melanosis/melanoma: utility of conjunctival map biopsy

Aim To assess the role of map biopsy in patients with conjunctival primary acquired melanosis (PAM)/melanoma. Methods Retrospective case series of 400 conjunctival biopsy samples of 51 unique patients in a tertiary referral centre. Results Each patient underwent one diagnostic biopsy and several additional map biopsies (range 2-7) providing a total of 400 samples for the analysis (55 diagnostic biopsies, 345 map biopsies). The median age was 63 years old (range 20-88) with women representing 67% of the cases. Histopathological findings were graded as negative for melanosis/normal (grade 0), melanosis without atypia (grade 1), melanosis with mild atypia (grade 2), melanosis with severe atypia (grade 3) or invasive melanoma (grade 4). Clinicopathologic concordance was observed in the majority of the map biopsies (313, 91%) (positive: clinical+/path+ (57,17%), negative: clinical-/path- (256, 74%)). Three discordant samples (clinical-/path+) represented PAM sine pigmento. The histopathological spectrum of atypia was absent (40, 73%) or limited (11, 20%) in the majority of cases with tendency to cluster as low-grade or high-grade atypia. Map biopsy led to the identification of six patients (11%) with severe atypia, requiring topical mitomycin (MMC). Similarly, in 29 cases, periodic observation without topical MMC was recommended. One case of invasive melanoma transformation occurred in the MMC-treated group. Conclusions Map biopsy enhances overall assessment of the anatomic and pathologic extent, impacting use of adjuvant topical chemotherapy. In absence of map biopsy, it would be impossible to diagnose PAM sine pigmento. Additional corroborative work is needed to validate our observations.