Histopathologic Patterns of Recurrent Choroidal Melanoma Following I-125 Plaque Brachytherapy

Abstract

Purpose: Histologic correlation of clinical patterns of recurrent choroidal melanoma following I-125 plaque brachytherapy was performed to identify pathologic mechanisms of recurrence. Methods: We reviewed 7 cases of recurrent choroidal melanoma following I-125 plaque brachytherapy managed with enucleation. Clinical characteristics included tumor dimensions, radiation dose, time to local recurrence, and clinical pattern of recurrence. Histopathology (hematoxylin and eosin and periodic acid – Schiff) and immunohistochemistry (Ki-67, CD-163, HMB45, and SOX10) were performed. Results: Mean follow-up time and time to local recurrence were 42 and 21 months after brachytherapy, respectively. Tumor recurrences were described clinically as marginal in 43%, diffuse in 29%, and extraocular extension (EOE) in 29%. Eighty-six percent were classified as mixed cell type and 14% were epithelioid type. Tumor zonation (histologic demarcation between zones of recurrent and nonrecurrent tumor cells by immunohistochemistry) was present in marginal and EOE cases (n = 6) and absent in the diffuse cases (n = 2). Ki-67 proliferative index was higher in marginal and EOE recurrences, while diffuse cases showed uniform ­Ki-67 staining. CD-163 staining was found to be greater in nonrecurrent tumor. HMB45 correlated with SOX10 with a greater staining in recurrent tumor. Conclusion: Our observations provide a correlation between histopathologic and clinical patterns of local recurrence of choroidal melanoma after brachytherapy.