PMC4317213_01
Clinical picture of a 3-year-old Rhodesian Ridgeback, which was presented with protrusion of the third eyelid. Upon inspection the enlargement of the nictitans and a temporodorsal deviation of the globe were present (A and B).
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fig01
Closer inspection revealed that the pigmented rim of the third eyelid was displaced ~0.5 cm away from the globe due to a mass, which was present in the entire visible bulbar aspect of the third eyelid (Fig.1).
The third eyelid and the mass appeared grossly to be completely removed by surgery (A) and was sent for histopathologic analysis (B and C).
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fig02
Following resection, grossly the mass seemed to be removed with clean margins (Fig.2).
Low power (A) and high power (B) photomicrographs of hematoxylin and eosin stained sections of the excised tumor within the nictitans. Arrows indicate mitotic figures. Bars: 200 mum (A) and 50 mum (B).
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fig03
Microscopic investigation revealed a mesenchymal, highly proliferative mass characterized by short interlacing streams, and bundles of closely packed spindle-shaped cells arranged in a storiform to herringbone pattern with few whorls (Fig.3).
Immunohistochemical staining of the tumor tissue. Virtually all cells were positive for vimentin (A) and up to 50% of the cells were positive for S-100 (B). Bars: 50 mum.
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fig04
The canthotomy wound was closed with a figure of eight suture (nylon 4/0, Ethilon ; Ethicon, Hamburg; Germany) and a temporary tarsorrhaphy was placed nasally (nylon 4/0 and two pieces of silicone tubing). Immunohistochemistry for vimentin, a marker staining intermediate filaments of mesodermal origin, found virtually in all the cells to be positive (Fig.4A). Additionally, up to 50% of the cells stained positive for S-100 (Fig.4B), indicating cells derived from the neural crest.