Infiltrating orbital granular cell tumour: a case report and literature review.

A surgical biopsy of an infiltrative retrobulbar mass in a 44-year-old man was diagnosed as granular cell tumour. Electron microscopy and immunoperoxidase stains were used to confirm the diagnosis and to study the histogenesis of this rare soft tissue neoplasm. S-100 stain was positive, while neuron-specific enolase and myoglobin stains were negative, suggesting a non-specific neural origin for the cells. The capability of this tumour to invade surrounding tissues has seldom been described in the orbit and is demonstrated by this case.