MACROSCOPIC DESCRIPTION:
An irregular grey tan nodule, 20x10x10mm. Inked blue and serially sectioned.
MICROSCOPIC DESCRIPTION:
Paraffin sections show a densely hypercellular tumour. This consists of cells with uniform round and oval vesicular nuclei with conspicuous nucleoli and a small amount of pale cytoplasm. These are arranged in irregularly shaped solid islands which are haphazardly dispersed in a dense fibrous stroma. A palisaded arrangement of tumour cells at the periphery of these islands is noted. Occasional mitoses are identified. No necrosis is seen. Immunohistochemistry shows strong staining in tumour cells for pancytokeratin AE1/AE3, BerEp4, synaptophysin, CDX2 and neurone specific enolase (NSE) and moderate staining for CD56. No staining for S-100 protein or TTF-1 is seen in tumour cells. The features are of carcinoid tumour. The topoisomerase labelling index is approximately 3%
FINAL DIAGNOSIS:Right orbital tumour: Carcinoid tumour
Primary carcinoid tumours of the orbit are rare. Those that have been reported have usually had a dural attachment. Metastatic carcinoid tumours usually have atypical features which this tumour lacks. Primary sites that should be excluded however include lung, caecum/appendix, small bowel and pancreas.