Primary pineal melanocytic tumor. Case report.

A primary melanocytic lesion arising from the pineal gland is very rare. The authors report a case of primary pineal melanocytic tumor with dissemination to the right hippocampus in a 50-year-old woman who presented with memory disturbance. Magnetic resonance (MR) imaging revealed a mass that was hyperintense on T1-weighted and hypointense on T2-weighted MR images. The pineal tumor was removed subtotally via the occipital transtentorial approach, and the patient underwent whole-brain irradiation. Results of histological examination revealed that the tumor predominantly consisted of atypical cells with scanty melanin pigment and some necrotic foci. The strongly pigmented areas of the tumor contained well-differentiated cells similar to those of melanocytoma. An ultrastructural study demonstrated evidence of a mature type of melanosome. The patient died 11 months after surgery and radiotherapy (1.7 years after the onset of symptoms). The autopsy findings demonstrated tumor invasion into the parenchyma through the leptomeningeal space and the ventricular wall. The tumor was diagnosed as being malignant, and it was finally concluded that the atypical cells in the tumor were probably responsible. This pineal melanocytic tumor exhibited a wide spectrum of differentiation, ranging from highly malignant melanoma to well-differentiated melanocytoma, which may have contributed to the patient's relatively long survival period. The biological behavior and morphological characteristics of this tumor appear to be similar to those of other pineal parenchymal lesions.