Ibizan Hound Case

Species: Canine
Breed: Ibizan Hound
Age: 9yr
Gender: Male

Source/History:

Ophthalmologist diagnosed cancer in globe of left eye.

Click here for the IDEXX Pathology Report on this case.

Microscopic Description:

Expanding and effacing the ciliary body and/or iris stroma, compressing and distorting the iris, obliterating the anterior and posterior chambers, adjacent to the anterior lens capsule, and occluding the filtration angle is a densely cellular, unencapsulated, relatively well demarcated, expansile, epithelial neoplasm. The neoplasm is composed of tubules with vague papillary projections, cords and islands of low cuboidal to polygonal cells, supported by a fine, fibrovascular stroma. Neoplastic cells have variably distinct cell borders, moderate amounts of granular, eosinophilic to clear cytoplasm and round to oval, usually hyperchromatic nuclei with a variably distinct nucleolus. Mitoses average <1 per 10 HPFs. There are scattered melanomacrophages and lymphocytes in the stroma. Multifocally, the anterior margin of the iris is adhered to the cornea (anterior synechia) and the drainage angle is occluded.

Microscopic Interpretation:

Interpretation:  Left globe: iridocillary adenoma, uveo-invasive type, well differentiated with secondary glaucoma and retinal detachment

Mitotic count: <1

Excision:  Completely removed, limited to the interior globe

Vascular Invasion: Not observed.

Comments:

Iridociliary epithelial tumors are the second most common intraocular neoplasm in dogs, and the fourth most common intraocular neoplasm in cats. It originates from the mature neuroectodermal cells of the pigmented and nonpigmented epithelial cells of the iris and ciliary body. Golden Retrievers and Labrador Retrievers account for 39% of the canine cases.

Adenomas can be non-invasive (limited to the anterior and posterior chambers) or uveo-invasive (invade the uveal stroma). Key differentiating feature of an iridociliary adenocarcinomas from an adenoma are the presence of pleomorphism, high mitotic index and invasion of the choroid and sclera. Malignant iridociliary epithelial neoplasm can be designated either as iridociliary adenocarcinoma or pleomorphic adenocarcinoma. Pleomorphic adenocarcinomas are long standing lesions that invade the whole globe. Whereas iridociliary adenocarcinomas are unlikely to metastasize, pleomorphic adenocarcinomas are likely to metastasize. In contrast to canine cases, approximately 30% of feline cases have osseous metaplasia. This neoplasm has a strong propensity to induce pre-iridal fibrovascular membrane.

Immunohistochemistry for vimentin, S-100 and NSE (neuron specific enolase) can help confirm the diagnosis. Overall, cytokeratin staining appears to increase with increasing aggressiveness of the neoplasm.

References:

Dubielzig et al. 2010. Veterinary Ocular Pathology: A Comparative Review. Saunders. pp. 291-295.
Maxie. (ed). 2007. Pathology of Domestic Animals. 5th edition. Vol 1. pp. 542.

Image Notes:

  1.  Low magnification view of the lesion, demonstrating a well demarcated, non encapsulated, multilobulated, mass expanding the iris.
  2. Higher magnification view of the lesion, demonstrating tubules with vague papillary projections, cords and islands of low cuboidal to polygonal cells, supported by a fine, fibrovascular stroma.
  3. Higher magnification view of the lesion, demonstrating tubules lined by well differentiated low cuboidal to polygonal cells.

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