Positivity to glial fibrillary acidic protein in bone, cartilage, and chordoma.

Twenty vertebral bones, 11 costal, 11 epiglottic, six tracheal, and five bronchial cartilages and seven chordomas were evaluated by the application of peroxidase-antiperoxidase (PAP) indirect immunohistochemical method for localization of glial fibrillary acidic protein (GFAP). Positive immunostaining for GFAP was observed in osteocytes of normal bone (13/20), chondrocytes of normal epiglottis (5/11), costal cartilage (3/11), trachea (2/6), and bronchus (4/5). Four of seven chordomas had neoplastic cells that exhibited cytoplasmic positivity to GFAP. These findings suggested that osteocytes, chondrocytes, and chordoma cells have cytoskeletal intermediate filaments that are antigenically identical to or similar to or associated with GFAP.