RIMARY pigmented lesions of the CNS are uncommon and range from melanosis of the leptomeninges to malignant melanoma. The term “meningeal melano- cytoma” was first proposed by Limas and Tio 10 in 1972 to describe a lesion that exhibits the microscopic features of a meningioma but the ultrastructural and immunohistochem- ical characteristics of a melanocytic tumor. We describe the first case of a histologically identified melanocytoma of the cerebellopontine angle that turned into a primary malignant melanoma within a short time. Case Report History and Examination. This 37-year-old woman pre- sented in the year 2000 with progressive brainstem syn- drome resulting from a previously discovered tumor that extended from the petroclival area to the anterior craniocer- vical junction. In 1988 she had undergone surgery during which, according to the pathological report, a “fibrous, me- lanocytic meningioma” in that region was subtotally re- sected. Detection of the Ki-67 antigen was not a routine diagnostic procedure at that time and, thus, in 2002 we performed an immunohistochemical analysis of the original specimen. Our analysis revealed a low level of proliferation according to Ki-67 staining (3% of cells stained with Ki-67) (Fig. 1 left). Repeated MR imaging examinations did not re- veal any sign of tumor progression until 2000, when com- pression of the brainstem was observed. Operations and Pathological Findings. Subtotal removal of a hard dark tumor was achieved in 2001. Histological and immunohistochemical examinations revealed the typ- ical features of a melanocytoma (expression of vimentin, HMB-45, S100 protein, and melan A) with increased pro- liferation (5% of cells stained with Ki-67) but only scant mitotic activity and absent necrosis (Fig. 1 center). The sparse amount of cells was enhanced with melanin-specific stains. Clinical deterioration as well as neuroimaging evidence of tumor progression led to another operation within 7 J Neurosurg 101:528–531, 2004 528 Transition from meningeal melanocytoma to primary cerebral melanoma Case report FLORIAN ROSER, M.D., MAKOTO NAKAMURA, M.D., ALMUTH BRANDIS, M.D., VOLKMAR HANS, M.D., PETER VORKAPIC, M.D., PH.D., AND MADJID SAMII, M.D., PH.D. Department of Neurosurgery, Klinikum Hannover Nordstadt; Institute of Pathology, Klinikum Hannover; Institute for Neuropathology and German Brain Tumor Reference Center, University of Bonn; and International Neuroscience Institute, Hannover, Germany √ The authors describe the first case of an intracranial transition of a melanocytoma into a primary malignant melanoma within a short time. A 37-year-old woman presented with progressive brainstem syndrome due to a tumor, originally di- agnosed and treated 12 years earlier, that extended from the petroclival area to the anterior craniocervical junction. The histological workup following subtotal tumor resection of the initial tumor had revealed the typical features of a fibrous melanocytic meningioma without increased proliferation. Ten years after the patient had completed treatment for the me- lanocytic meningioma, control neuroimaging demonstrated growth of the residual tumor with compression of the brain- stem. Another neurosurgical intervention revealed a dark tumor of hard consistency. At this time immunohistochemical examinations demonstrated melanocytic features (expression of vimentin, S100 protein, and melan A) of the lesion with focally increased proliferation (5% of Ki-67–positive cells) but no higher mitotic activity. Clinical signs of deterioration along with imaging-confirmed tumor progression precipitated another operation within 7 months. A neuropathological ex- amination revealed epithelial and anaplastic changes and indicated that the MIB-1 indices were greater than 25%. Pleo- morphic changes and a focal high mitotic activity led to the diagnosis of a primary cerebral malignant melanoma. The pa- tient’s later clinical course consisted of a rapid diffuse meningeal spread of the lesion throughout the entire brain and spine. Despite whole-brain and stereotactic radiation therapy as well as chemotherapy, the patient died 4 months after the last neuropathological diagnosis. Although grossly resembling a meningioma, melanocytomas lack the former’s histological and immunohistochemical features. The biological behavior of a melanocytoma is variable and recurrence may happen after subtotal resection, but intracranial transition into a malignant melanoma has not been observed previously. KEY WORDS • brain neoplasm • melanocytoma • melanoma • meningioma P J. Neurosurg. / Volume 101 / September, 2004 Abbreviations used in this paper: CNS = central nervous system; MR = magnetic resonance.