Uveal schwannoma in a brown‐eyed dog

An eleven‐year‐old, female spayed Boxer dog was diagnosed with a uveal schwannoma (formerly known as the spindle cell tumor of the blue‐eyed dog or SCTBED) despite having a uniformly brown iris. The patient presented to emergency for ocular discomfort, and the right globe was subsequently enucleated due to glaucoma and submitted for histopathology. Upon histopathologic evaluation, a uveal schwannoma was diagnosed and confirmed with immunohistochemical staining. Complete metastatic evaluation 1 and 6 months after initial presentation did not reveal evidence of metastasis, and the dog remains systemically healthy. This case represents a unique variant of uveal schwannoma and is relevant because although the vast majority of these tumors occur in blue‐eyed dogs, clinicians should not completely rule out this tumor as a differential based on the iris color.     

Intraocular peripheral nerve sheath tumor in a dog

A tumor within the right globe in a 9-year-old Shetland sheepdog was examined pathologically. The tumor was composed of spindle or oval cells arranged in interwoven bundles with intervening collagenous or mucinous matrices. Immunohistochemically, the tumor bound antibody directed to S-100 protein and vimentin, but not to desmin, actin smooth muscle, or neurofilament. Electron microscopy revealed that the tumor cells had poorly developed cytoplasmic processes, desmosomes between closely contiguous cells, and a discontinuous basement membrane-like material. Based on these findings, the tumor was diagnosed as a peripheral nerve sheath tumor (PNST) histologically. To the authors' knowledge, this is the first reported case of intraocular PNST in dogs.     

Ocular myxoid leiomyosarcoma in a cat

A case of myxoid leiomyosarcoma likely of iris dilator muscle origin in the enucleated eye of a 6-year-old domestic short haired cat is reported. The poorly demarcated mass expanded the iris, partially filled the globe and extended into the optic nerve. The mass was composed of spindle cells separated by abundant matrix positive for mucopolysaccharides with alcian blue. The neoplastic cells were immunoreactive for smooth muscle actin (SMA), S100 and vimentin, and negative for cytokeratin, Melan-A, glial fibrillary protein (GFAP) and desmin. There was no evidence of recurrence or metastasis 6 months after enucleation.     

Bilateral uveal metastasis of a subcutaneous fibrosarcoma in a cat

A 6‐year‐old neutered male domestic short‐haired cat was presented to the Comparative Ophthalmology service at Michigan State University with a 3‐week history of decreased appetite and redness of the left eye. The left forelimb had been removed 15 months previously because of the presence of a subcutaneous fibrosarcoma. In the left globe, a large iridal mass was associated with increased intraocular pressure and retinal detachment. A smaller mass involving the right iris was also present. Imaging revealed a 2‐cm mass in the left caudodorsal lung lobe, and abdominal ultrasound showed multifocal bilateral renal masses. Aspirates of these masses were nondiagnostic. The left globe was removed for palliative reasons, and histopathology showed that fibrosarcoma was infiltrating the iris, choroid, and optic nerve. Despite systemic chemotherapy with doxorubicin, the animal died 4 months after initial presentation. Histopathology confirmed highly angioinvasive metastatic fibrosarcoma also in the right uveal tract, the lungs, and both kidneys.     

Unusual presentation of a metastatic uveal melanoma in a cat

A 10 year-old, spayed female Domestic Short-Haired (DSH) cat was diagnosed with a large primary uveal melanoma and exenteration was recommended. Thoracic radiographs, abdominal ultrasonography, and complete blood count and serum biochemistry panel did not reveal any abnormality compatible with metastatic disease and surgery was performed. Histopathologic study of the eye confirmed a diffuse iris melanoma. Five months later, the cat presented with a lameness of the right anterior extremity. On physical exam the right elbow was swollen and painful. Radiographs showed a severe osteolysis of the radial head and proximal diaphysis. Fine needle aspiration of the radius head identified a round cell neoplasm with scattered cells containing intracytoplasmatic pigmented granules, compatible with metastatic melanoma. The owners decided not to treat the patient with chemotherapy and declined a biopsy. Two months later, the cat died and necropsy was performed confirming bone metastasis of the uveal melanoma. A diagnosis of generalized metastasis from primary diffuse iris melanoma was made. This report describes, for the first time, long bone metastasis from an uveal melanoma in a cat.     

Glaucoma associated with uveal cysts and goniodysgenesis in American Bulldogs: a case series

We present a series of three American Bulldogs with clinical signs of glaucoma and intraocular inflammation accompanied by bilateral uveal cysts and abnormal gonioscopic findings. All dogs proved refractory to medical management and were enucleated. Histopathologic findings were similar in all three and included significant preiridal fibrovascular membranes and mononuclear inflammatory infiltrates in the anterior uvea. On microscopic evaluation, cysts appeared to arise primarily from the ciliary body and iridociliary sulcus, with smaller cysts also budding from the posterior iris. Pigment dispersion was variable but consistent, involving deposition of a small number of pigment‐laden cells in the dependent trabecular meshwork. Cataract formation was not noted. Glaucoma associated with uveal cysts has been described previously in Golden Retrievers and Great Danes, although clinical and histopathologic findings in those breeds are not identical to those described here. American Bulldogs with uveal cysts should have gonioscopy performed and should be monitored carefully for signs of increased intraocular pressure and intraocular inflammation. Furthermore, documentation of cyst‐associated glaucoma in a third breed suggests clinicians should exercise caution in dismissing uveal cysts in dogs as incidental findings.     

Presumed post‐traumatic ocular chondrosarcoma with intrathoracic metastases in a cat

An indoor‐only, 5‐year‐old, spayed female domestic shorthair cat presented for an ophthalmic examination of the left eye. An intraocular tumor with secondary glaucoma and blindness was diagnosed; the globe was enucleated and sent for histopathological examination. Gross examination revealed a solid white mass filling the entire vitreous space and replacing the iris and ciliary body. The lens and retina appeared to be similarly replaced by the neoplasm. Histological examination revealed a complete loss of the internal ocular structures, with a ruptured capsule as the only remnant of the lens within an extensive malignant mesenchymal neoplastic cell proliferation. The cells were polygonal, with well‐defined cytoplasmic borders and abundant weakly basophilic cytoplasm, embedded within the islands of chondroid matrix. No neoplastic invasion of the sclera was apparent. The animal died 6 months after the enucleation due to respiratory distress. Gross examination revealed numerous firm, white to tan nodular masses with smooth to mildly irregular surfaces dispersed throughout the parietal pleura, thoracic surface of the diaphragm, tracheobronchial and mediastinal lymph nodes, pericardium, and lungs. On cross‐section, the neoplastic nodules were solid and variably translucent, resembling hyaline cartilage. Histologically, these nodules were similar to the neoplasm identified earlier in the left globe. Metastasis of post‐traumatic ocular chondrosarcoma has not yet been described in cats. This is therefore believed to be the first report of metastases of this type of neoplasm in cats. This case adds to the limited set of data on the outcome of this type of tumor.     

Suspected uveal metastasis of a nail bed melanoma in a dog

A 13-year-old Golden Retriever was referred for evaluation of generalized corneal edema, dyscoria, and suspected glaucoma affecting the right eye. The dog exhibited no signs of systemic illness, but had a history of a melanoma of the nail bed of the first digit of the right hind limb, excised 1 year previously. Ophthalmologic examination revealed diffuse corneal edema, mild anterior uveitis, glaucoma and a mass within the right iris. Enucleation was performed and histopathologic evaluation of the globe revealed the iris to be infiltrated with an anaplastic melanoma, suspected to represent a metastasis of the original nail bed tumor.     

ULTRASONOGRAPHIC FEATURES OF CANINE GASTROINTESTINAL STROMAL TUMORS COMPARED TO OTHER GASTROINTESTINAL SPINDLE CELL TUMORS

Canine gastrointestinal stromal tumors (GISTs) are a recent subtype of gastrointestinal spindle cell tumor recognized with the increasing use of immunohistochemistry. To our knowledge, no imaging features have been described in immunistochemically confirmed canine GISTs. The objective of this retrospective, cross‐sectional study was to describe ultrasonographic features of canine GISTs compared with other spindle cell tumors. Thirty‐seven dogs with an ultrasonographically visible gastrointestinal mass and a histopathologic diagnosis of spindle cell neoplasia were examined. Immunohistochemistry staining was performed for retrieved tissue samples to further differentiate the tumor type and each sample was interpreted by a single veterinary pathologist. Ultrasonographic features recorded examined included mass echogenicity, homogeneity, presence of cavitation, layer of origin, bowel wall symmetry, and loss of wall layering, location, size, vascularity, and evidence of perforation or ulceration. Tumor types included 19 GISTs, eight leiomyosarcomas, six leiomyomas, and four nonspecified sarcomas. Gastrointestinal stromal tumors were significantly more likely to be associated (P < 0.03) with abdominal effusion than other tumor types. There was overlap between the anatomical locations of all tumors types with the exception of the cecum where all eight tumors identified were GISTs. Besides location, there were no unique ultrasound features of GISTs that would allow distinction from other gastrointestinal spindle cell tumors. Similar to previous studies, GISTs appeared to be the most common spindle cell tumor associated with the cecum in our sample of dogs. The high frequency of abdominal effusion with GIST's was of unknown etiology could possibly have been due to septic peritonitis.     

Of all the nerve! A subcutaneous forelimb mass on a cat

A 16-year-old, male, neutered cat had a 2.5 X 1.5 cm mass on the medial aspect of the right carpus. Cytologic examination of a fine-needle aspirate of the mass indicated a markedly pleomorphic population of plasmacytoid to histiocytic-appearing cells. The cytologic diagnosis was malignant neoplasia of probable mesenchymal or round cell origin. The right forelimb was surgically removed and the scapular, axillary, and prescapular lymph nodes were excised. Malignant fibrous histiocytoma was tentatively diagnosed histologically; however, the tumor cells subsequently were found to be negative for histiocytic (MAC 387, antitrypsin), T-cell (CD3), and B-lymphocyte (immunoglobulin light chains, Ly 5/CD45R) markers, and positive for glial fibrillary acidic protein, vimentin, and S-100. Based on the immunohistochemical results, the diagnosis was modified to malignant peripheral nerve sheath tumor (PNST). Six months after surgery, the cat was reported to be well and had no evidence of metastasis. PNSTs are rare tumors in cats, and are considered as synonymous with schwannomas, neurofibrosarcomas, and hemangiopericytomas. In this cat, the plasmacytoid and pleomorphic appearance of the PNSTcells in cytologic and histologic specimens was unusual, and made it difficult to reach an accurate diagnosis without immunocytochemistry.     

Schwannoma of the External Auditory Canal in a Filly: A Case Report

Schwannomas of the external auditory canal (EAC) are exceedingly rare in human beings and domestic animals. Herein we describe the clinicopathological and immunohistochemical features of a benign schwannoma arising in the EAC of a 2.5-year-old filly. Microscopically, the mass showed a spindle cell tumor composed of hypocellular Antoni type B areas as a myxomatous arrangement of mesenchymal cells and hypercellular Antoni type A areas displaying short fascicles of densely packed neoplastic cells in the collagenous stroma. Immunohistochemically, the tumor cells were diffusely positive for S100 protein and vimentin but negative for Ki67. It was concluded that schwannomas should be included in the differential diagnosis of EAC masses, and immunohistochemical markers such as S100 protein can strongly help in differentiating this tumor from other spindle cell tumors.     

Prevalence of ophthalmic disease in blue‐eyed horses

A perception exists amongst referring veterinarians and the lay public that blue‐eyed horses have increased frequency of ocular disease. The aim of this retrospective study was to assess the prevalence of ocular disease in horses with blue or heterochromic eyes relative to those with brown eyes. The medical records of horses presenting to either the Comparative Ophthalmology services or Equine Medicine/Surgery services at 2 institutions were reviewed. Signalment, ocular and nonocular diagnoses were recorded. Ocular disease was divided into 4 categories: adnexa, cornea, intraocular/orbit and squamous cell carcinoma (SCC). Owners were contacted by telephone to confirm iris colour. Chi‐square analysis was used to compare group proportions. A total of 164 eyes of horses with ocular disease and 212 eyes of horses without ocular disease were included. Blue eyes were equally common in the ocular disease and nonocular disease groups (P = 0.265). There was no significant difference in the proportion of blue‐ and brown‐eyed horses when comparing the adnexal and corneal (P = 0.548), corneal and intraocular/orbit (P = 0.379) and adnexal and intraocular/orbit (P = 0.843) categories. A significant difference was detected in the proportion of blue‐eyed horses between the adnexal (P = 0.000), corneal (P = 0.033), intraocular/orbital (P = 0.000) and SCC categories, with a higher proportion of blue‐eyed horses in the SCC than in the other 3 groups. Horses with blue or heterochromic irides are more likely to develop ocular SCC than horses with brown irides, but are not more likely to have adnexal, corneal or intraocular/orbital disease or to be presented for evaluation of ophthalmic disease. Veterinarians should consider the results of this study when answering questions from the lay public regarding the predisposition of blue‐eyed horses to ocular disease.     

MALIGNANT PERIPHERAL NERVE SHEATH TUMOR IN A CAT

A report of a cat with a cranial tumor of nerve sheath origin is presented. The cranial mass, with a cyst-like character on presentation to the referring veterinarian suggested a benign lesion, but the clinical course was rapid and indicative of central nervous system involvement. The tumor was poorly differentiated by histologic examination, but immunohistochemistry was consistent with Schwann cell origin. Features of peripheral nerve sheath tumors in cats and other species are briefly discussed.     

Intraocular and orbital malignant schwannomas in F344 rats.

Intraocular and orbital malignant Schwannomas in two F344 rats are presented. The two Schwannomas were identified among approximately 60,000 male and 60,000 female F344 rats. The intraocular malignant Schwannoma occurred in the iris, invading the corneal stroma through the destroyed Descemet membrane. The malignant orbital Schwannoma occurred in the left orbit, invading the contralateral orbit along the optic nerve. Histologically, the intraocular Schwannoma consisted predominantly of a perivascular fascicular pattern of plump spindle cells associated with marked cytoplasmic vacuolization. The orbital Schwannoma consisted of Antoni type A and B pattern, but Antoni B tissues predominated. Antoni A tissues consisted of closely packed, elongated spindle cells arranged in interlacing fascicles, while Antoni B tissues were highly cellular and consisted of anaplastic, small cells associated with marked cyst formation. Immunohistochemically, the intraocular Schwannoma had a positive immunoreactivity for S-100 protein, while the orbital Schwannoma had a negative immunoreactivity. Ultrastructurally, the cells of both intraocular and orbital Schwannomas had long, thin cell processes and pericytoplasmic basal laminae. Particularly, the plump spindle cells of the intraocular Schwannoma were most strikingly characterized by the well developed, extremely attenuated cell processes arranged in a lamellar or spiral pattern. These cell processes and cell bodies were associated with numerous desmosomes. Intracytoplasmic filamentous granules and bodies, consisting of intermediate filaments approximately 7 nm in width, were additional characteristics of the plump spindle cells.     

Feline periocular peripheral nerve sheath tumor: a case series

The objective of this retrospective study was to describe signalment, clinical presentation, surgical treatment, outcome, histopathologic, and immunohistochemical characteristics of periocular peripheral nerve sheath tumor in a series of cats. Six cats with a histologic diagnosis of peripheral nerve sheath tumor of the eyelid and/or conjunctiva were identified from 3997 feline ocular histopathologic submissions to the Comparative Ocular Pathology Laboratory of Wisconsin between 1976 and 2002. Medical records were reviewed and data were collected for signalment, eye affected, location, duration, and history of tumor recurrence. Ancillary diagnostic tests, surgical approach, and histopathology were also described. Special stains and immunohistochemistry panels were performed on the tissue. Follow-up information was obtained through telecommunications with the owner and local veterinarian. The mean age of the cats was 8 years (range: 5-15 years). There was an equal distribution of males and females. Breeds represented were two Domestic Long-haired (DLH) cats, three Domestic Short-haired (DSH) cats, and one Manx. The right eye was affected in four cats and the left eye in two cats. The superior eyelid was affected in four cats, the superior conjunctiva in two cats, and the inferior eyelid in one cat. All of the cats that underwent surgical excision, cryoablation, or laser ablation had an average of three recurrences of the tumor. Four of six cats undergoing wide excision with enucleation, exenteration or rhomboid flap had no recurrence of the tumor. Histomorphologically, all of the tumors were of spindle cell type with five of six tumors showing histologic features of Antoni type B tissue. All six tumors stained positive for vimentin. Five of six tumors stained positive for S-100 and laminin. All six tumors were negative for smooth muscle actin. Definitive histologic diagnoses of spindle cell tumors can be difficult. The presence of Antoni A and B histologic patterns as well as immunohistochemical reactivity for vimentin, S-100, and laminin suggest a diagnosis of peripheral nerve sheath tumor. Our findings suggest that local aggressive recurrence is common and that wide surgical excision combined with enucleation or exenteration may be indicated.     

Clinical behavior of intraocular teratoid medulloepithelioma in two‐related Quarter Horses

The objective of this paper is to describe clinical behavior, histopathologic features, and immunohistochemical staining of two‐related horses with intraocular teratoid medulloepithelioma. Two‐related Quarter Horses with similar intraocular masses presented to the UF‐CVM Comparative Ophthalmology Service for evaluation and treatment. The first horse, a 3‐year‐old gelding, had glaucoma and a cyst‐like mass in the anterior chamber. Enucleation was performed. Histopathology revealed a teratoid medulloepithelioma. The tumor was considered to be completely excised. Fifteen months later, the gelding presented with swelling of the enucleated orbit and local lymph nodes with deformation of the skull. Cytology revealed neuroectodermal neoplastic cells. Necropsy confirmed tumor metastasis. Six weeks later, a 9‐year‐old mare, a full sibling to the gelding, presented for examination. An infiltrative mass of the iris and ciliary body was found that extended into the anterior, posterior, and vitreal chambers. Uveitis was present, but secondary glaucoma was not noted. Enucleation was performed and the histopathologic diagnosis was also teratoid medulloepithelioma. The mare has had no recurrence to date, 2 years following enucleation. Metastasis of intraocular teratoid medulloepithelioma is possible. Staging is recommended in cases where the diagnosis of teratoid medulloepithelioma is confirmed. Surveillance of full siblings is recommended until more information regarding etiology is known.