A retrospective study of lingual lesions in 793 dogs and 406 cats at the Athens Veterinary Diagnostic Laboratory, 2010-2020.

Lingual biopsies are a common type of sample submission at the Athens Veterinary Diagnostic Laboratory (AVDL). Here we describe the pathology diagnoses of 793 canine and 406 feline lingual biopsies submitted to the AVDL in a 10-y period. Non-neoplastic lesions accounted for 450 diagnoses (57%) in dogs and 239 diagnoses (59%) in cats. Canine non-neoplastic lesions consisted of inflammatory lesions (286 cases; 64% of non-neoplastic lesions) and tumor-like proliferative lesions (164 cases; 36% of non-neoplastic lesions). Feline non-neoplastic lesions consisted of inflammatory lesions (228 cases; 95% of non-neoplastic lesions) and tumor-like proliferative lesions (11 cases; 5% of non-neoplastic lesions). The most common canine neoplasms were melanocytic neoplasms (103 cases; 30% of neoplasms) and epithelial neoplasms (102 cases; 30% of neoplasms), followed by mesenchymal neoplasms (90 cases; 26% of neoplasms) and round cell neoplasms (48 cases; 14% of neoplasms). Approximately 43% of melanocytic neoplasms affected Chow Chows and Labrador Retrievers, and 20% of epithelial neoplasms affected Labrador Retrievers. In cats, most tumors were epithelial (158 cases; 94% of neoplasms), followed by mesenchymal (8 cases; 5% of neoplasms) and round cell neoplasms (1 case; 1% of neoplasms). Over 50% of neoplasms of cats affected domestic shorthair cats. Although the percentage of lingual biopsies that had a neoplastic diagnosis was roughly the same between species, the diversity of neoplasms was much greater in dogs than in cats.

Comparison of fluorescent antibody test, immunohistochemistry, and PCR testing for diagnostic confirmation of neurolisteriosis in 25 goats.

Neurolisteriosis, a common disease of small ruminants, is most often caused by Listeria monocytogenes. Here we describe 25 cases of caprine neurolisteriosis diagnosed in our laboratory over a 5-y period and compare our fluorescent antibody test (FAT) results with immunohistochemistry (IHC) and polymerase chain reaction (PCR) testing for diagnostic confirmation. Neurohistologic changes consistent with neurolisteriosis affected the pons in all cases, extending rostrally to the mesencephalon in 6 cases, caudally to the medulla oblongata in 6 cases, and/or dorsally to the cerebellum in 4 cases. Acute inflammatory changes were observed in 17 cases, and included neuroparenchymal microabscesses, neuronal necrosis and neuronophagia, axonal swelling, microgliosis and astrogliosis, and perivascular neutrophils with macrophages, lymphocytes, and plasma cells that occasionally extended to the leptomeninges. Subacute-to-chronic changes (8 cases) consisted of neuroparenchymal and perivascular clusters of macrophages with rare neutrophils, lymphocytes, and plasma cells admixed with glial nodules. Bacterial bacilli were observed within neutrophils or macrophages in H&E-stained tissue sections in 4 cases. Gram stain highlighted gram-positive bacilli in 13 cases. Neurolisteriosis was confirmed by FAT in 2 cases, by IHC in 19 cases, and by PCR in 20 cases.

Rostral cranial fossa and sinonasal neoplasms with cribriform plate involvement in 32 dogs and 17 cats.

The rostral cranial fossa (RCF) consists of the sphenoid and ethmoid bones, which accommodate the olfactory bulbs and nerves along the recesses of the cribriform plate. Neoplasms located in the vicinities of the RCF can compress and/or invade the cribriform plate. Here we describe the clinical and pathologic findings of neoplasms involving the cribriform plate in 32 dogs and 17 cats autopsied over a 13-y period. The average ages of affected dogs and cats were 9.2 y and 9.7 y, respectively. No sex or breed predisposition was evident in dogs, but 13 of 18 cats were spayed females and 14 of 18 were domestic shorthair cats. The main clinical signs were seizures (10 cases) and epistaxis (5 cases) in dogs, and red-to-brown nasal discharge (5 cases) and seizures (4 cases) in cats. In dogs, the 22 sinonasal neoplasms included adenocarcinoma (14 cases), transitional carcinoma (4), squamous cell carcinoma (2), lymphoma (1), and histiocytic sarcoma (1); the 10 intracranial neoplasms consisted of high-grade gliomas (3 cases), psammomatous meningiomas (2), histiocytic sarcomas (2), olfactory neuroblastomas (2), and a meningeal granular cell tumor (1). In cats, the 14 sinonasal neoplasms included lymphoma (8 cases), adenocarcinoma (4), adenosquamous carcinoma (1), and squamous cell carcinoma (1); the 3 intracranial neoplasms consisted of oligodendroglioma (1), transitional meningioma (1), and olfactory neuroblastoma (1).

The artifact of cerebellar granule cell layer conglutination in veterinary medicine: a brief historical perspective and review.

Cerebellar granule cell layer conglutination is a tissue artifact associated with postmortem autolysis that causes cerebellar granule cell changes once thought to be caused by degeneration and necrosis. Granule cell layer conglutination has been reported mainly in humans and cattle and rarely in other animal species, but its frequency remains vastly unknown in veterinary medicine, mostly because this postmortem change is typically not recorded in autopsy reports. Pathology trainees should be aware of autolytic tissue changes that may mimic pathologic changes in the CNS, particularly when those changes are highly selective for a specific cell population within the cerebellar cortex. Here we provide a brief historical perspective on the evolution of cerebellar granule cell layer conglutination from "enzootic cerebellar necrosis," a presumed necrotic lesion affecting granule neurons in humans and cattle, to a tissue change associated with postmortem autolysis and increased tissue acidity in the cerebellum. We also provide an update on the animal species in which cerebellar granule cell layer conglutination has been observed during our diagnostic pathology routine.

Dermal melanoma with plasmacytoid differentiation in a dog.

A 10-y-old spayed female Staffordshire Terrier dog was evaluated because of a cutaneous left ear base mass. Cytology revealed sheets of cells with anisocytosis and anisokaryosis, round-to-oval or plasmacytoid cytoplasm, and round, central, or eccentric nuclei; binucleate cells were present. Cytologic findings were consistent with a round cell tumor (plasmacytoma or agranular mast cell tumor), amelanotic melanoma, or anaplastic carcinoma. Histologically, neoplastic cells were polygonal to elongate, with round-to-oval nuclei and prominent nucleoli and arranged in sheets and nests on a fibrovascular stroma. Neoplastic cells with plasmacytoid morphology (round, glassy, eosinophilic cytoplasm with eccentric nuclei) were present in ~30% of the neoplasm. There were 18 mitoses in 2.37 mm2 (10 FN22/40× fields). Neoplastic cells had cytoplasmic immunolabeling for melan A and PNL2 and no immunolabeling for AE3/1 and MUM1, consistent with a dermal melanoma with plasmacytoid differentiation. The patient was re-evaluated ~1 mo after the first biopsy because of local recurrence of the original mass and new masses on the interscapular area and right elbow; these neoplasms were histologically identical to the original submission, plus scattered neoplastic cells in the new masses contained brown cytoplasmic pigment. The dog was euthanized because of swelling and hemorrhage of the tumors and right pelvic limb lameness. Our findings were consistent with a dermal melanoma with plasmacytoid features that were similar to human plasmacytoid melanoma, a rare variant of human melanoma that is diagnostically challenging as it may mimic a plasmacytoma.

Rosettes and pseudorosettes in veterinary neuropathology.

Rosettes and pseudorosettes are morphologic cell arrangements found in many neuroepithelial neoplasms in human medicine, including embryonal nervous system tumors (neuroblastoma, medulloblastoma, pineoblastoma, and retinoblastoma), non-embryonal nervous system tumors (ependymoma, astrocytoma, oligodendroglioma, and choroid plexus tumors), and other extraneural neuroepithelial neoplasms. Although these structures are also described in neuroepithelial neoplasms of domestic animals, their frequency is still poorly characterized or inconsistently documented in veterinary medicine. Furthermore, rosettes and pseudorosettes need to be interpreted with caution and within a clinical and pathologic context and should not be solely relied upon for diagnostic confirmation of a particular neoplasm. Here, we review the morphologic features and frequency of the most common types of rosettes and pseudorosettes described in neuroepithelial neoplasms of domestic animals, focusing primarily on those occurring in the nervous system and closely associated tissues.

Oral fibrolipoma in dogs: Retrospective case series study and comparative review.

Fibrolipoma is defined as a typical lipoma transected by variable amounts of paucicellular and collagenous fibrous components. Oral and lingual fibrolipomas are well-recognized histological entities in human medicine that are slightly more prevalent in females, occur most commonly after the fourth decade, and arise from the buccal mucosa. The documentation of this neoplasm in the oral cavity is lacking in veterinary medicine. Through a multi-institutional retrospective compilation of cases submitted to diagnostic pathology services, here we describe the clinical and pathologic features of oral fibrolipomas in dogs. A total of 112 cases of oral fibrolipomas in dogs were retrieved. The mean age was 10.1 years (range 2-16 years, ±2.63 years standard deviation), with an average tumor size of 1.7 cm (range 0.2-8 cm, ±1.1 cm standard deviation). The most common location was the tongue (57.1%, 64/112), followed by the buccal mucosa (15.2%, 16/112), sublingual area (8.0%, 9/112), gingiva and lip (4.5%, 5/112 each), and palate (1 case). The anatomical location of oral fibrolipomas only differed significantly among the dog breeds (P < .001) but not among sex, age, anamnesis, or reason for submission. The tumor was most commonly reported in males (69.7%, 78/112), and in 62.5% (70/112) of the cases, the tumor was an incidental finding. Fibrolipoma should be considered a differential diagnosis when considering benign lingual and other oral soft tissue masses in dogs.

Cytokeratin AE1/AE3 immunolabeling in epithelioid hemangiosarcoma.

Epithelioid hemangiosarcoma (EH), a rare histological variant of hemangiosarcoma, is reported in various animal species, including humans, dogs, cows, horses, and cats. Epithelioid hemangiosarcomas are composed of highly pleomorphic epithelioid cells arranged in cords, islands, nests, or solid cellular areas, similar to epithelial neoplasms. Moreover, in humans, approximately 50% of EHs have cytoplasmic immunolabeling for cytokeratin AE1/AE3 (CK AE1/AE3), making it challenging to distinguish them from carcinomas. This retrospective study assessed the CK AE1/AE3 immunolabeling in canine EH cases from 5 veterinary institutions. Immunohistochemistry for CD31 and CK AE1/AE3 was performed on 30 cases. CK AE1/AE3 immunolabeling was detected in 43% (13/30) of cases, with cytoplasmic labeling ranging from 5% to 100% of neoplastic cells. All tumors consistently had membranous immunolabeling for CD31. The CK AE1/AE3 immunolabeling pattern in canine EHs closely resembled those documented in humans, indicating a similar diagnostic challenge. Therefore, it is recommended to include a vascular immunohistochemistry marker, such as CD31, whenever EH is suspected, particularly in small incisional cutaneous and subcutaneous biopsies.

Development of a Model of Tubulointerstitial Fibrosis Using Transient Unilateral Renal Ischemia and Delayed Contralateral Nephrectomy in Domesticated Cats.

Tubulointerstitial fibrosis is a classic histologic feature of chronic kidney disease (CKD) in cats and a final common pathway toward end-stage renal disease. Domesticated cats have been used in models of ischemia-induced renal fibrosis. The objective of this study was to evaluate the performance of 2 variations of a transient unilateral renal ischemia and delayed contralateral nephrectomy model of tubulointerstitial fibrosis in cats. Purpose-bred, young adult, domesticated cats underwent 90 min of surgically induced ischemia to the right kidney followed by delayed contralateral nephrectomy performed 21 d (RI-CN21d group; n = 10) or 90 d postischemia (RI-CN90d group; n = 12). Control cats underwent sham surgery followed by left nephrectomy 21 d after (sham-CN group; n = 3). Renal functional parameters, including glomerular filtration rate and serum creatinine concentration, were evaluated before and after surgeries. The right kidneys were harvested 120 d postischemia/ sham. Renal histology with lesion scoring and histomorphometry for quantification of smooth muscle actin immunolabeling and collagen staining were performed on harvested kidneys. Severe acute kidney injury prompted euthanasia after left nephrectomy in 5/10 (50.0%), 2/12 (16.7%), and 0/3 (0%) of cats in the RI-CN21d, RI-CN90d, and sham-CN groups, respectively. A significant decrease in glomerular filtration rate by day 120, relative to baseline, occurred in cats in the RI-CN21d group (P < 0.001) and RI-CN90d group (P < 0.001) but not the sham-CN group (P = 0.76). All but one cat in the ischemia groups were azotemic at the study end. Kidneys subjected to ischemia had higher interstitial inflammation, tubular atrophy, and fibrosis scores compared with sham-operated kidneys. There were significant increases in smooth muscle actin immunolabeling and collagen staining in these kidneys, relative to the contralateral kidneys. In summary, 90 min of unilateral renal ischemia and delayed contralateral nephrectomy induced histologic and biochemical changes consistent with CKD in cats. A 90-d period between ischemia and nephrectomy resulted in improved survivability of the model.

Canine glioma in the first year of life: 5 cases.

Most canine gliomas occur in adult and aged dogs, and reports in puppies < 12-mo-old are exceedingly rare. Here we describe the occurrence of gliomas in 5 dogs ≤ 12-mo-old. The affected patients (4 males, 1 female) were 3-12-mo-old (x̄ = 6.6-mo-old). None of the dogs were brachycephalic. Clinical signs consisted of dullness (2 cases), seizures (2 cases), vestibular signs, and deafness (1 case each). All patients were euthanized. Grossly, neoplasms were pale-tan or red, soft masses in the telencephalon (4 cases) or gelatinous leptomeningeal thickening in the brain and spinal cord (1 case). Neoplasms were classified as astrocytomas (3 cases) and oligodendrogliomas (2 cases) based on histology or histology and IHC. Our findings confirm that, while exceptionally rare, canine gliomas occur in the first year of life, and are clinically, morphologically, and immunohistochemically similar to gliomas in adult and aged dogs.

Diagnostic immunohistochemistry of primary and secondary central nervous system neoplasms of dogs and cats.

The diagnosis of primary and secondary CNS neoplasms of dogs and cats relies on histologic examination of autopsy or biopsy samples. In addition, many neoplasms must be further characterized by immunohistochemistry (IHC) for a more refined diagnosis in specific cases. Given the many investigations assessing the diagnostic and prognostic IHC profile of CNS neoplasms in the veterinary literature, it may be difficult for the diagnostic pathologist or pathology trainee to narrow the list of reliable diagnostic IHCs when facing a challenging case. Here we compile a comprehensive list of the most diagnostically relevant immunomarkers that should be utilized for the diagnostic support or confirmation of the most common primary and secondary CNS neoplasms of dogs and cats.

Effects of autolysis and prolonged formalin fixation on histomorphology and immunohistochemistry of normal canine brain tissue: an experimental study.

CNS tumor diagnosis in dogs often relies on immunohistochemistry (IHC) given similar histologic features among tumors. Most CNS tissue samples encountered by diagnostic pathologists are collected during autopsy, and postmortem specimens can be susceptible to autolysis and prolonged formalin fixation, both of which have the potential to influence IHC results and interpretation. Here we evaluated the effects of experimentally controlled autolysis induced by delayed tissue fixation (sections of brain held for 2, 4, 8, 12, 24, 48, and 72 h in 0.9% NaCl at either room temperature or 37°C prior to fixation) as well as the effects of prolonged formalin fixation times (1 wk, 1 mo, 2 mo) on a panel of 8 IHC markers (CNPase, GFAP, Iba1, OLIG2, PGP9.5, MAP2, NeuN, synaptophysin) relevant to brain tumor diagnosis. Prolonged fixation of up to 2 mo had no detrimental effect on any immunomarker except NeuN, which had reduced immunolabeling intensity. Delayed fixation led to autolytic changes as expected, on a gradient of severity corresponding to increased time in saline prior to fixation. Several immunomarkers should be used with caution (CNPase, OLIG2) or avoided entirely (MAP2, NeuN) in markedly autolyzed brain and brain tumor tissues. Our results suggest that autolysis has minimal effect on most immunomarkers, but that advanced autolysis may cause a loss of specificity for GFAP, MAP2, and PGP9.5, a loss of intensity of CNPase and OLIG2, and loss of labeling with MAP2 and NeuN. Prolonged fixation affected only NeuN, with mildly decreased intensity.

Primary and secondary leptomeningeal gliomatosis in dogs.

Leptomeningeal gliomatosis (LG) is characterized by extensive dissemination of neoplastic glial cells in the subarachnoid space either without an intraparenchymal glioma (primary LG or PLG) or secondary to an intraparenchymal glioma (secondary LG or SLG). Given the low frequency of LG in human and veterinary medicine, specific diagnostic criteria are lacking. Here, we describe 14 cases of canine LG that were retrospectively identified from 6 academic institutions. The mean age of affected dogs was 7.3 years and over 90% of patients were brachycephalic. Clinical signs were variable and progressive. Relevant magnetic resonance image findings in 7/14 dogs included meningeal enhancement of affected areas and/or intraparenchymal masses. All affected dogs were euthanized because of the poor prognosis. Gross changes were reported in 12/14 cases and consisted mainly of gelatinous leptomeningeal thickening in the brain (6/12 cases) or spinal cord (2/12 cases) and 1 or multiple, gelatinous, gray to red intraparenchymal masses in the brain (6/12 cases). Histologically, all leptomeningeal neoplasms and intraparenchymal gliomas were morphologically consistent with oligodendrogliomas. Widespread nuclear immunolabeling for OLIG2 was observed in all neoplasms. The absence of an intraparenchymal glioma was consistent with PLG in 3 cases. The remaining 11 cases were diagnosed as SLG.

Case report: Surgical treatment of an astrocytoma in the thoracic spinal cord of a cat.

A 15-year-old spayed female domestic shorthaired cat was evaluated for chronic progressive paraparesis and proprioceptive ataxia. Neurological examination was consistent with a T3-L3 myelopathy. Plain thoracolumbar vertebral column radiographs and CT without intravenous contrast or myelography performed at another facility did not highlight any abnormalities. MRI of the thoracolumbar spinal cord identified an intraparenchymal space-occupying lesion extending from T10-T12. Surgery was performed to remove as much of the mass as possible, and to submit samples for histopathology. A dorsal laminectomy was performed over T9-T13. A midline myelotomy provided access to the mass, which was debrided with an intraoperative estimate of 80% removal. Histopathologic examination was consistent with a diagnosis of an astrocytoma. Post-operative treatment consisted of amoxicillin clavulanic acid, prednisolone, gabapentin, and additional analgesic medications in the direct post-operative period. Over the following 4 months, slow recovery of motor function was seen with continued physiotherapy. During the following 2 months, renal and cardiopulmonary disease were diagnosed and treated by other veterinarians. The cat was also reported to have lost voluntary movement in the pelvic limbs during this period, suggesting regression to paraplegia. Finally, 6 months post-surgery, the owner elected humane euthanasia. This is the second documentation of surgical treatment and outcome of an astrocytoma in the spinal cord of a cat.

Glioma with cribriform plate involvement in 6 dogs.

Distinct patterns of local infiltration are a common feature of canine oligodendroglioma and astrocytoma, and typically involve the surrounding neuroparenchyma, ventricles, or leptomeninges. Infiltration of adjacent extraneural sites is rare and has not been well documented in veterinary medicine. Here we describe 6 canine gliomas with cribriform plate involvement (compression or infiltration) and caudal nasal invasion confirmed by neuroimaging, autopsy, and/or histology. All affected dogs were adults (9-12-y-old), and 3 were brachycephalic. Clinical signs were associated with the brain tumor, with no respiratory signs reported. Magnetic resonance imaging in 2 patients revealed a rostral intraparenchymal telencephalic mass with extension into the cribriform plate. All dogs were euthanized. Gross changes consisted of poorly demarcated, white or pale-yellow, soft, and, in oligodendrogliomas, gelatinous, intraparenchymal masses that expanded the rostral portions of the telencephalon and adhered firmly to the ethmoid bone and cribriform plate. Gliomas were classified as high-grade oligodendrogliomas (4 cases) and high-grade astrocytomas (2 cases) based on histology and immunohistochemistry for OLIG2 and GFAP. In all cases, there was evidence of cribriform plate invasion and, in one case, additional invasion of the caudal nasal cavity.

Intracranial inflammatory polyp with cerebellopontine compression and leptomeningitis secondary to chronic otitis in a red kangaroo.

CNS lesions associated with chronic otitis have not been reported in red kangaroos (Macropus rufus), to our knowledge. Here we describe an intracranial inflammatory polyp secondary to chronic otitis in a 6-y-old female red kangaroo with right auricular discharge, loss of balance, and head tilt. Autopsy highlighted a pale-yellow, firm, intracranial polypoid growth that extended from the right tympanic cavity through the internal acoustic meatus and intracranially, with compression of the right cerebellopontine angle. Anaerobic bacterial culture yielded Bacteroides pyogenes from fresh brain and a right external ear swab. Histologically, the tympanic cavity was effaced by neutrophils and macrophages surrounded by lymphocytes and plasma cells, as well as edematous fibrovascular tissue. The epithelial lining of the mucoperiosteum was hyperplastic, with epithelial pseudoglands surrounded by fibrovascular tissue. Areas of temporal bone lysis and remodeling were associated with the inflammatory changes, which occasionally surrounded adjacent nerves. Fibrovascular tissue and inflammatory cells extended from the tympanic cavity through the internal acoustic meatus and into the intracranial cavity, forming the polypoid growth observed grossly; the polyp consisted of a dense core of fibrovascular tissue with scattered clusters of neutrophils and foamy macrophages. Lymphocytes and plasma cells surrounded the leptomeningeal perivascular spaces in the brainstem, cerebellum, and occipital lobe.