Case Study: March 2011

1. Granular cell tumour (GCT) of the orbit. This is a benign tumour of peripheral nerve sheath origin which rarely undergoes malignant change. It has been reported in the orbital soft tissues, particularly involving the extraocular muscles. Granular cell tumours are infiltrative lesions with an ill-defined margin consisting of polygonal or spindle shaped cells which have a characteristic eosinophilic granular cytoplasm and bland nuclei (Figure 1: HE x10).Chronic inflammatory infiltrates have been reported in association with GCT and in this case, occurred as lymphoid aggregates.
2. Although the microscopic appearance of GCT is distinctive, the differential diagnosis of this tumour may include atypical histiocytic inflammatory lesions and the presence of the lymphocytic infiltration may be misleading.
3. Granular cell tumours are immmunoreactive to S100 (Figure 2) and CD68 (Figure 3) and are negative for epithelial, melanocytic, smooth muscle, dendritic cell, and endothelial markers. These tumours are also PAS positive and diastase resistant.

References

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2. Poyraz CE, Kiratli H, Söylemezo?lu F.Korean J Ophthalmol. 2009 Mar;23(1):43-5. Granular cell tumor of the inferior rectus muscle.
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