Primary Choroidal Melanoma with Divergent Neuroendocrine Differentiation

Primary Choroidal Melanoma with Divergent Neuroendocrine Differentiation

Background: Despite well-defined histopathological characteristics, melanoma has been reported to have different histological and immunohistochemical variations that can lead to diagnostic controversy. Neuroendocrine divergent differentiation has been demonstrated previously in skin and metastatic melanoma, and also in metastatic tumors to the choroid, but not in primary choroidal melanoma.
Aim: To report the clinical, histopathological, immunohistochemical and ultrastructural characteristics of four cases of primary choroidal melanoma with neuroendocrine differentiation.
Methods and Results: A retrospective case series analysis was conducted for all patients with choroidal melanoma with confirmed histopathological features of neuroendocrine differentiation, evaluated at the Laboratory of Ophthalmic Research and Visual Sciences. Four cases were identified, two male and two female. Preoperative clinical diagnosis was choroidal melanoma for all cases. Atypical small-cell morphology distributed in a pattern forming an organoid, perivascular or nested architecture on light microscopy was found in all cases, which prompted further evaluation with neuroendocrine markers. Immunohistochemistry demonstrated positivity in at least three melanocytic and three neuroendocrine markers for each case. Hi-resolution optic microscopy showed granules corresponding to intracytoplasmic neurosecretory and melanin granules in the same cells, confirming the diagnosis.
Conclusions: In this study we provide evidence suggestive of divergent neuroendocrine differentiation in primary choroidal melanoma.