Peripheral primitive neuroectodermal tumor of the orbit in Graves' ophthalmopathy - A rare presentation.

Graves' ophthalmopathy is the most common cause of both unilateral and bilateral proptoses in adults. Peripheral primitive neuroectodermal tumor (pPNET) is a small round cell malignant lesion of neuroectodermal origin which very rarely affects the orbit. In this case report, we have discussed about a young woman with existing Graves' ophthalmopathy who presented with worsening proptosis; computed tomography imaging revealed an irregular mass lesion in the right orbit without bone erosion. Biopsy and immunohistochemistry of the mass lesion revealed features of primitive neuroectodermal tumor (PNET). The tumor was MIC-2 gene positive, and on follow-up, no recurrence was noted after successful surgical resection. PNET of the orbit is very rare, and to our best knowledge, this is the first case of peripheral PNET in patent with Graves' ophthalmopathy.