Pulse - September 2021 - 24

PRACTICAL PATHOLOGY
Canine Uveal Schwannoma
Farshid Shahriar DVM, PhD, Dipl ACVP - Lore Laboratory, Tustin, CA
Medical History and clinical findings:
Enucleated eye from an adult, 6 year-old, female-spayed dog submitted for histopathological
examination. Patient had history of glaucoma.
Gross and Histopathologic findings:
Grossly, there was a growth in anterior chamber between the lens and filtration angle. (Fig.
1) Histologically, The globe exhibits evidence of a completely excised, expansile and infiltrative
uveal Schwannoma with marked expansion of the uveal stroma by a monomorphic
population of small spindle-shaped neoplastic cells arranged in streams, bundles, and fascicles
often with palisading nuclei and Antoni A and Antoni B patterns.(Fig. 2) Plump neoplastic
spindle cells have moderate amounts of amphophilic cytoplasm and indistinct cell borders.
Nuclei are oval with clumped chromatin and 1 or 2 dense nucleoli. Anisocytosis and
anisokaryosis is mild and there are 2 mitotic figures/10 high power fields. Centrally, there is
marked, acute, caseous necrosis in this grade 2 neoplasm. There is no extension into the sclera
or surrounding peripheral nerves. Neoplastic cells have occluded the ciliary cleft and iridocorneal
angle (Fig. 3). There is evidence of secondary glaucoma with loss of retinal ganglion
cells and atrophy of the inner nuclear layer. There is multifocal, mild to moderate, subacute,
lymphoplasmacytic inflammation in the uveal shwannoma and anterior uveitis, scleritis and
peripheral keratoconjunctivitis. There is mild nuclear sclerosis in the lens with no cataract
formation or phacolysis is noted.
Diagnosis:
Diagnosis of uveal schwannoma with mild to moderate anterior uveitis, scleritis and secondary
glaucoma was made.
Discussion:
Uveal schwannomas of blue-eyed dogs have been reported in adult canines and were
first described in 2007 with the former name spindle cell tumor of blue-eyed dogs. The
preponderance of GFAP-positive cells in the blue uvea is believed to predispose blue eyed
dogs to uveal schwannoma formation. The significant increase in linear iridal GFAP positivity
is consistent with non-myelinated nerves in blue eyed dogs. Immunohistochcemistry
characterizes further. Research for a possible genetic defect in neural crest development
contributing to oncogenesis in this tumor (particularly in Siberian Huskies) is underway.
Ultraviolet radiation may play a role but this has not been substantiated to date. Rare
extension into surrounding peripheral nerves has been reported in a similar canine uveal
schwannoma from a juvenile, not blue eyed dog. Complete surgical excision is often a cure
with rare metastasis noted to the liver, mesenteric lymph nodes and lungs in a dog in one
report. There is evidence of glaucoma secondary to this neoplasm obstructing the filtration
angle as is oftentimes noted in affected dogs. The cause of uveitis present may be metabolic,
immune-mediated, drug induced, traumatic or it may due to glaucoma/ high intraocular
pressure-associated anterior segment ischemia and uveitis is noted in all dogs with
uveal schwannoma in one report. It has been noted in the globes of many of the dogs with
this type of neoplasm. P
*
Figure 2
Figure 1
Figure 3
24
SEPTEMBER 2021
PULSE

Pulse - September 2021

Table of Contents for the Digital Edition of Pulse - September 2021

Pulse - September 2021
Chapter Meetings & Calendar
President’s Perspective
Pulsepoints
SCVMA Profile
How Veterinary Managers’ Jobs Differ
Practical Pathology
Medical Leeway
UC Davis Update
Tools for Success
Angel Fund
Dear Tabby
The RVT
Industry Insights
Quick Reference
AVMA Diplomates
Digital Photography for Veterinarians
Resources
Disease Table
From the SCVMA Office
Pulse - September 2021 - Pulse - September 2021
Pulse - September 2021 - Cover2
Pulse - September 2021 - 1
Pulse - September 2021 - 2
Pulse - September 2021 - Chapter Meetings & Calendar
Pulse - September 2021 - President’s Perspective
Pulse - September 2021 - Pulsepoints
Pulse - September 2021 - 6
Pulse - September 2021 - 7
Pulse - September 2021 - 8
Pulse - September 2021 - 9
Pulse - September 2021 - 10
Pulse - September 2021 - SCVMA Profile
Pulse - September 2021 - How Veterinary Managers’ Jobs Differ
Pulse - September 2021 - 13
Pulse - September 2021 - 14
Pulse - September 2021 - 15
Pulse - September 2021 - 16
Pulse - September 2021 - 17
Pulse - September 2021 - 18
Pulse - September 2021 - 19
Pulse - September 2021 - 20
Pulse - September 2021 - 21
Pulse - September 2021 - 22
Pulse - September 2021 - 23
Pulse - September 2021 - Practical Pathology
Pulse - September 2021 - Medical Leeway
Pulse - September 2021 - UC Davis Update
Pulse - September 2021 - Tools for Success
Pulse - September 2021 - 28
Pulse - September 2021 - Angel Fund
Pulse - September 2021 - Dear Tabby
Pulse - September 2021 - The RVT
Pulse - September 2021 - Industry Insights
Pulse - September 2021 - Quick Reference
Pulse - September 2021 - AVMA Diplomates
Pulse - September 2021 - Digital Photography for Veterinarians
Pulse - September 2021 - 36
Pulse - September 2021 - 37
Pulse - September 2021 - 38
Pulse - September 2021 - Resources
Pulse - September 2021 - 40
Pulse - September 2021 - Disease Table
Pulse - September 2021 - 42
Pulse - September 2021 - 43
Pulse - September 2021 - 44
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Pulse - September 2021 - From the SCVMA Office
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