In vivo confocal microscopy of pigmented conjunctival tumors.

Purpose: To analyze the appearance of conjunctival pigmented tumors as seen by in vivo confocal microscopy.

Methods: Twenty-eight pigmented conjunctival tumors including 6 nevi, 13 acquired melanoses, 7 conjunctival melanomas, and 2 extrascleral growths of uveal melanomas were examined by in vivo confocal microscopy using the Heidelberg Retina Tomograph (HRTII)/Rostock Cornea Modul (RCM). Confocal images were analyzed using predefined criteria by an observer masked to final histological diagnosis and a preliminary diagnosis was established. After excision, histology and immunohistochemistry using antibodies against S-100, Melan-A, HMB-45, Ki-67, CD3, and CD68 were performed in all specimens and compared with in vivo confocal images of the same lesions.

Results: Confocal microscopy images confirmed typical histopathological features of conjunctival pigmented tumors. Nest or diffuse collections of medium-sized uniform hyper- or hyperreflective cells in the stroma and stromal cysts lined with a multilayered epithelium were visible in 100% of conjunctival nevi. Small dendritic cells were typically observed in 100% of primary acquired melanoses (PAM) without atypia and in 2 out of 6 nevi. Large networks of hyperreflective dendritic cells were present in 100% of PAM with atypia. Whereas images of PAM without atypia and secondary complexion-associated melanosis showed hyperreflective granules confined to the basal epithelium in 67% of lesions, PAM with atypia presented with hyperreflective granules and patches throughout the epithelium in all cases. Malignant melanomas of the conjunctiva and extrascleral growths of uveal melanomas demonstrated large hyperreflective cells with prominent nuclei and nucleoli. In vivo confocal microscopy showed a sensitivity of 89% and a specificity of 100% to establish the correct diagnosis of conjunctival melanoma compared with histology.

Conclusions: High correlations were found between in vivo confocal microscopy using near-infrared laser light and histology in the diagnosis of pigmented conjunctival lesions. In vivo confocal microscopy seems to be a valuable new tool in the differential diagnosis and follow-up of pigmented conjunctival tumors. It does not replace histology, but may assist in performing guided biopsy in tumors suspected clinically and/or with in vivo microscopy. In addition, in vivo confocal microscopy may support the clinical diagnosis of extrascleral involvement in uveal melanoma.