Glial fibrillary acidic protein immunoreactive cells in osteosclerotic bone marrow of a patient with malignant glioma

Glial fibrillary acidic protein (GFAP) is used widely as a specific marker of astrocytes, in part because GFAP‐positive cells have rarely been encountered outside the central nervous system. In this paper we describe a 16‐year‐old female with a brain stem glioblastoma and GFAP immunoreactive cells in areas of bone marrow with osteosclerotic changes. These GFAP cells were negative for S‐100 and devoid of cell atypism, showing non‐neoplastic features. To investigate the factors which might be involved in the induction of GFAP in the non‐neoplastic cells, we examined the expression of cytokines and growth factors in the bone marrow. Immunoreactivities of interleukin‐1β (IL‐1β) and tumor necrosis factor‐α (TNF‐α) were found to be reduced. In contrast, those of epidermal growth factor receptor (EGFR) were increased. Glial fibrillary acidic protein expression with decreased IL‐1β and TNF‐α and increased EGFR in bone marrow may be related to the pathogenesis of progressive osteosclerosis found in this patient with brain stem glioblastoma.