Basal ganglion hamartoma in a patient presenting with precocious puberty.

We report a basal ganglion hamartoma in a 10-year-old boy in whom the major clinical feature was precocious puberty. Endocrinological evaluation showed a gonadotropin reaction to luteinizing hormone-releasing hormone with no elevation of the human chorionic gonadotropin beta-subunit level in the serum or cerebrospinal fluid. Neuroimaging studies showed a small, calcified, nonenhanced mass lesion with some cystic components in the right basal ganglion. Histopathological examination of specimens removed by stereotactic needle biopsy revealed disorganized neuronal and glial elements in the calcified gray matter-like lesion. In addition, although the presence of microcalcifications was not conspicuous, similar neuroglial lesions of various sizes were scattered in the surrounding white matter. Immunostaining for Ki-67 antigen (MIB-1) showed very low proliferative potential of the glial cells in all the lesions. To our knowledge, this is the first reported occurrence of an intracranial hamartoma located in a site other than the hypothalamus and causing precocious puberty. The possible mechanisms underlying the development of precocious puberty in this patient are discussed.