Today's Veterinary Practice

NOV-DEC 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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FEATURES NOVEMBER/DECEMBER 2018 41 based on multiple factors, including the suspected tumor type, evidence of metastatic disease, secondary complications, and overall patient health. Enucleation is indicated when the patient has intractable secondary uveitis, glaucoma, or ocular discomfort unresponsive to medications or when the goal is to obtain a diagnosis. Patients with severe uveitis obscuring a definitive diagnosis may warrant aggressive medical treatment with topical and systemic anti- inflammatories before definitive therapy. Treatment can help clear anterior chamber hemorrhage and inflammation to enable direct examination of the eye, which may reveal an obvious mass and prompt enucleation. Even in the absence of an obvious mass, discomfort and secondary glaucoma may prompt enucleation and submission of the globe for histopathology. For tumors that have extended outside the globe, exenteration (removal of the globe and surrounding orbital tissues) may be recommended. Any enucleated eyes or locally excised tumors should be submitted for histopathology to determine the type of neoplasm and whether any further treatment (e.g., chemotherapy or radiation) is recommended. Treatment by enucleation is controversial for the many dogs that have melanocytic uveal tumors in an eye that is still functional (i.e., can see) and that have no evidence of inflammation and glaucoma. Some practitioners elect to monitor apparent uveal melanomas because of their slow progression and low risk for metastasis. Some melanocytic tumors are amenable to laser photocoagulation. 5 Laser photocoagulation can be performed with endolaser, transscleral, or transcorneal diode or Nd:YAG laser and is best suited to focal tumors with no extension into the iridocorneal angle. To preserve vision in dogs with no secondary complications, local excision of a mass with iridectomy or iridocyclectomy procedures has been described. 11 Clients interested in vision-sparing surgical or laser treatment options for their pet should be referred to an ophthalmologist for further evaluation. CATS As for dogs, the most common primary intraocular tumor of cats is iris melanoma. Generally, cats with melanocytic lesions are brought to the veterinary clinic for iris color change or for iris melanosis, which is benign. Uveal cysts, although less common in cats than in dogs, can also mimic melanoma, and methods for differentiation are similar. 12 The second most common tumor in cats is posttraumatic sarcoma ( FIGURE 4A AND 4B ), which is incited by ocular trauma and inflammation (e.g., trauma to the lens, chronic uveitis, and gentamicin injections into the posterior segment for ciliary body ablations). 1,13–16 This tumor is specific to cats. Specific tumor types reported include fibrosarcoma, osteosarcoma, and undifferentiated sarcoma. 17 These tumors are postulated to arise from malignant transformation of lens epithelium, a process that has not been reported for other species, and they share similarities with feline vaccine-induced sarcomas because both apparently result from an initial insult and subsequent chronic inflammation. 18 Although iridociliary epithelial adenomas and adenocarcinomas are rare in cats, they have been reported. 4 FIGURE 4. (A) Gross image of a large, pink, vascular mass and associated fibrin in the anterior chamber of a cat. (B) B-mode ultrasonography image from the same patient, demonstrating an extensive mass in the anterior chamber (arrow) as well as invading the posterior chamber (asterisk). Histopathologic diagnosis after enucleation was undifferentiated sarcoma. B A *

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