Primary Pineal Melanoma with Leptomeningeal Spreading: Case Report and Review of the Literature

Objective: Primary melanomas of the pineal region are exceedingly rare and may be difficult to diagnose. Clinical, radiological and pathological features as well as diagnostic procedures are discussed. CASE HISTORY We report herein on a 44-year-old man who presented with uncontrolled epileptic seizures. Magnetic resonance imaging revealed a pineal mass hyperintense on T1-weighted and isointense on T2-weighted sequences with diffuse leptomeningeal involvement and intense homogeneous contrast enhancement after gadolinium administration. A frontal leptomeningeal and cortical biopsy was performed. Histological examination showed a malignant melanocytic tumor cell proliferation expressing Melan-A, but not HMB-45 or S100 protein. Even if we have no proof that the tumor actually arose in the pineal gland, based on the radiological and histological findings, and on the unremarkable dermatologic and ophthalmologic examinations, a primary pineal melanoma with leptomeningeal dissemination was diagnosed. The patient received temozolomide-based chemotherapy followed by whole brain irradiation. The patient died 52 weeks after disease onset and 13 weeks after treatment initiation.

Conclusion: A diagnosis of pineal melanoma should be considered in the presence of a pineal mass that appears hyperintense on T1-weighted images and hypo- to isointense on T2-weighted images. The diagnosis is provided by pathological examination of tumor specimens obtained at surgical resection or at leptomeningeal biopsy. However, immunochemistry using anti-Melan-A, -S100 protein and/or -HMB45 antibodies on cerebrospinal fluid and leptomeningeal samples may be helpful in diagnosing such a disease. The prognosis of primary pineal melanoma is variable but meningeal spreading carries a dismal prognosis. The best therapeutic management is yet to be defined.