Primary Intraventricular Amelanotic Melanoma: Case Report and Literature Review.

Primary amelanotic melanoma of the central nervous system (CNS) represents an exceedingly rare neoplasm within the category of primary CNS melanocytic tumors. The absence of melanin pigmentation often complicates its identification, necessitating histopathological and immunohistochemical evaluation for accurate diagnosis. We describe the case of a 70-year-old man who presented with Parkinsonian features and was found to have a well-circumscribed intraventricular mass in the left atrium of the lateral ventricle (38×45×29 mm), hypointense on T1-weighted MRI with heterogeneous enhancement. Surgical resection was performed via a trans-intraparietal sulcus approach. Histopathology confirmed amelanotic melanoma, supported by immunopositivity for S-100, Melan-A, and HMB-45. The patient received adjuvant whole-brain radiotherapy followed by immunotherapy with nivolumab and ipilimumab. Although he initially improved, tumor recurrence occurred within five months, and treatment-related hepatotoxicity ultimately resulted in fatal hepatic failure one year after surgery. This case highlights the diagnostic challenges and aggressive behavior of primary intraventricular amelanotic melanoma. Even with gross total resection and multimodal therapy, the prognosis remains poor. Early recognition and multidisciplinary management are essential in addressing this rare entity.