Subependymal giant cell astrocytoma: a clinicopathologic study with HMB45 and MIB-1 immunohistochemical analysis

Subependymal giant cell astrocytomas (SEGAs) occur in approximately 6% of patients with tuberous sclerosis (TS) and are often considered to be a forme fruste or partial expression of this disorder. Recently, a number of other TS-associated lesions, including pulmonary and uterine lymphangiomyomatosis, renal angiomyolipoma, and cardiac rhabdomyoma, were shown to stain with the monoclonal antibody HMB45, suggesting a pathogenetic relationship among these lesions. Seven SEGAs in six patients (three men and three women; age range, 2-55 yr; mean, 24 yr) were studied. Cutaneous and other central nervous system features of TS were present in two patients. All of the SEGAs were intraventricular in location and were characterized by large, round, eosinophilic and spindle-shaped cells, with nuclear pseudoinclusions and mild nuclear pleomorphism, arranged in a vaguely perivascular pattern. All of the SEGAs were negative with HMB45 immunostaining. MIB-1 immunostaining was also performed in all of the cases, and MIB-1 indices (the percentage of MIB-1-positive nuclei) ranged from 0.1 to 3.8 (mean, 1.1). Two patients required an additional surgical procedure for residual/recurrent tumor; three patients are alive without evidence of disease 5 to 11 years after diagnosis; and one patient was lost to follow-up. SEGAs are generally slowly growing intraventricular neoplasms, as evidenced by their low MIB-1 labeling. Unlike other TS-associated lesions, SEGAs do not stain with HMB45.