p63 immunoexpression in hair follicles of normal and alopecia X-affected skin of Pomeranian dogs.

BACKGROUND: Alopecia X in Pomeranians is caused by a hair cycle deregulation, associated with downregulation of key regulatory genes of the Wnt and Shh pathways, and stem-cell markers. However, the pathogenesis remains unclear. p63 is an important transcription factor correlated with the aforementioned hair cycle modulating genes. HYPOTHESIS/OBJECTIVES: The aim of this study was to highlight possible changes of p63 immunohistochemical expression within the hair follicles in canine alopecia X compared with normal skin. ANIMALS: Skin biopsies from 19 alopecia X-affected and six control Pomeranians were analysed. MATERIALS AND METHODS: Serial histological sections of skin biopsies harbouring anagen, telogen and kenogen hair follicles were immunohistochemically evaluated for differences in p63 expression in the affected and control samples. RESULTS: Dogs with alopecia X had a significantly decreased immunoexpression of p63 in telogen and kenogen hair follicles. CONCLUSIONS AND CLINICAL RELEVANCE: The decrease of p63 immunoexpression observed in canine alopecia X suggests an involvement of p63 in hair cycle.

Canine and feline in situ mammary carcinoma: A comparative review.

Carcinoma in situ of the breast is a well-known entity in humans. In veterinary medicine, particularly in canine and feline mammary literature, there is no agreement whether the term in situ should be used to indicate a specific carcinoma histotype or the noninvasive status of a carcinoma of any histotype. Moreover, in the most recent histologic classification of mammary tumors published by the Davis-Thompson Foundation, it is suggested to abandon the term carcinoma in situ given the lack of standardized criteria defining this entity, replacing it with epitheliosis or ductal/lobular hyperplasia with severe atypia. This publication presents a critical review of the term in situ in human and veterinary medicine considering the evolution of the term over the years and its heterogeneous use by different authors, including variations in immunohistochemical markers for classification. This review aims to point out the lack of uniformity in the nomenclature and classification issues in veterinary medicine regarding the use of the term in situ, laying the ground for a process of standardization in future publications.

Evidence of avian poxvirus and papillomavirus infection in Gyps fulvus in Italy.

The identification of avian poxvirus and avian papillomavirus associated with cutaneous lesions in griffon vultures (Gyps fulvus) by histopathology, electron microscopy and PCR analysis is reported. Sequence analysis of the fpv140 gene revealed 99% identity to two poxviruses obtained from a white-tailed sea eagle (Haliaeetus albicilla) and a common buzzard (Buteo buteo). Partial sequence of the papillomavirus L1 gene showed sequence similarity to papillomavirus LI genes from African grey parrot (Psittacus erithacus) (69% identity), duck (Anas platyrhynchos) (68% identity), and yellow-necked francolin (Francolinus leucoscepus) (66% identity). To date, this is the first identification of avian poxvirus and papillomavirus in griffon vultures and the first evidence of infection of both viruses in live wild birds.

Survivin and Sox9: Potential Stem Cell Markers in Canine Normal, Hyperplastic, and Neoplastic Canine Prostate.

Canine prostatic carcinoma is a relevant model for human prostatic carcinoma. Survivin is proposed as a biomarker of malignancy in human prostatic cancer. Sox9 is a stem cell marker required for prostate development and expressed in several adult tissues. The aims of the present study were to evaluate the patterns and expression levels of 2 putative stem cell markers, survivin and Sox9, in canine benign prostatic hyperplasia (BPH) and prostatic carcinoma to investigate their potential as stem cell markers. Immunohistochemistry with specific antibodies was performed on 3 samples of normal prostate gland, 18 samples of canine BPH, and 16 samples of prostatic carcinoma. The basal cell layer of normal and hyperplastic prostatic lobules had nuclear Sox9 immunolabeling and nuclear and rarely cytoplasmic survivin immunostaining, identifying them as potential stem cell markers. Significantly more frequent survivin and Sox9 expression (≥10% of nuclei) was observed in prostatic carcinoma as compared with BPH. The potential coexpression of survivin with Sox9, androgen receptor, and p63 was also investigated in selected BPH and prostatic carcinoma cases with immunofluorescence, and a partial colocalization was observed. Results indicate that Sox9 and survivin could be considered markers of stemness in canine prostate cells. Given its role in proliferation, cells in the basal cell layer with nuclear survivin expression are likely to be transit-amplifying cells that maintain some stem cell proprieties.

Negative hepatic computed tomographic attenuation pattern in a dog with vacuolar hepatopathy and hepatic fat accumulation secondary to cushing's syndrome.

This report describes an unusual computed tomographic (CT) hepatic pattern, characterized by negative attenuation values (from -19.59 to -28.85 Hounsfield Units, HU) in a canine patient with severe Cushing's syndrome. Attenuation values of the splenic parenchyma (63.26 HU) and abdominal fat (-118.34 HU) were within normal limits. The negative hepatic attenuation values allowed a CT diagnosis of severe hepatic fatty infiltration that was subsequently confirmed by tissue-core biopsy and histopathological examination.

Canine cutaneous melanocytic tumours: significance of ß-catenin and survivin immunohistochemical expression.

BACKGROUND: Recent investigations have highlighted the controversial role of Wnt/ß-catenin pathway activation in human cutaneous melanoma. Survivin has been proposed as a valid prognostic marker for invasive and metastatic melanomas and lymph node melanoma metastasis in human cutaneous melanoma and is a promising therapeutic target. HYPOTHESIS/OBJECTIVES: Our aim was to investigate the immunohistochemical expression of survivin and ß-catenin in canine cutaneous melanocytic tumours, in order to understand their prognostic significance. METHODS: Twenty-one melanocytic tumours (10 melanocytomas and 11 melanomas) were investigated by immunohistochemistry using specific anti-survivin and anti-ß-catenin antibodies. A semi-quantitative method was used to analyse the results; ß-catenin immunolabelling in neoplastic cells was evaluated as cytoplasmic, membranous or nuclear. The number of survivin-positive cells was counted within ~1000 neoplastic cells. Results were related to histopathological features, evaluated in haematoxylin- and eosin-stained slides, and to the clinical data obtained through a telephone survey with referring veterinarians. RESULTS: Despite a low level of expression in the majority of cases, ß-catenin was found to be correlated strongly with malignant behaviour (P < 0.01). An overexpression of nuclear survivin was statistically related to histological features of malignancy, presence of metastasis and death related to melanoma spread (P < 0.01). CONCLUSIONS AND CLINICAL IMPORTANCE: The low nuclear ß-catenin expression, mainly found in metastatic cases, would indicate that ß-catenin activation may have only limited importance in the development or progression of canine cutaneous melanoma. The correlation of nuclear survivin expression with malignancy would indicate that survivin is possibly a useful prognostic marker and therapeutic target in canine melanoma patients.

Pathology survey on a captive-bred colony of the Mexican Goodeid, nearly extinct in the wild, Zoogoneticus tequila (Webb & Miller 1998).

The Mexican Goodeid, Zoogoneticus tequila, is considered nearly extinct in the wild and it is maintained in captivity by the nonprofit international "Goodeid Working Group." The unique Italian colony has produced about 180 fish so far. The observable diseases were registered and some fish were submitted, immediately after spontaneous death, to necroscopic and histopathologic exams. Encountered diseases included the following: 7 cases of scoliosis (2 males and 5 females); 2 fish with a similar congenital deviation of ocular axis; 1 adult male with left corneal opacity, presumably of traumatic origin; 1 female fish with a large subocular fluid-filled sac, histologically referable to a lymphatic cyst, similarly to the eye sacs of a Goldfish variety (Carassius auratus) called bubble eye; and 1 female fish with recurrent abdominal distension consequent to distal bowel dilation and thinning, associated with complete mucosal atrophy, and comparable to intestinal pseudo-obstruction syndromes described in humans and various animal species. The absence of infectious or parasitic diseases, as well as the low incidence of diseases potentially related to environmental alterations or nutritional disorders such as spinal deformities, suggests the adequacy of breeding management techniques of Z. tequila for its conservation and reintroduction in to the original habitat in the near future.

Epithelial-to-mesenchymal transition: immunohistochemical investigation of related molecules in canine cutaneous epithelial tumours.

BACKGROUND: Epithelial-to-mesenchymal transition (EMT) is a multistep process, important in tumour invasion and metastasis, characterized by loss of epithelial markers, redistribution of ß-catenin and gain of mesenchymal markers. HYPOSTHESIS/OBJECTIVES: Our aim was to investigate the immunohistochemical aberrant expression of cytokeratin, vimentin, survivin and heat shock protein 72 (Hsp72) in canine cutaneous epithelial tumours, to understand the association of expression of these molecules with features of malignancy and their role in the EMT phenotype. METHODS: Ten canine squamous cell carcinomas (SCCs; one with lymph node metastasis), 30 canine hair follicle tumours (six pilomatricomas, eight infundibular keratinizing acanthomas, six trichoepitheliomas and 10 trichoblastomas) and five normal skin samples were investigated by immunohistochemistry using specific anti-vimentin, -cytokeratin, -survivin and -Hsp72 antibodies. A semi-quantitative method was used to analyse the results, as follows: 0 to <5%; ≥ 5 to <10%; ≥ 10 to <25%; and ≥ 25% of positive cells. Immunofluorescence was performed to investigate survivin-vimentin and survivin-Hsp72 colocalization in selected SCCs. Results - In malignant hair follicle tumours and SCCs, a reduced intensity of cytokeratin and increased survivin and Hsp72 expression were observed. In SCCs, loss of cytokeratin expression and vimentin immunolabelling, suggestive of the EMT phenotype, were evident in <5% of neoplastic cells in the front of tumour invasion. In the same areas, strong nuclear survivin and cytoplasmic Hsp72 staining was evident, often colocalizing. Only a few neoplastic cells in the front of tumour invasion showed vimentin-survivin colocalization. CONCLUSIONS AND CLINICAL IMPORTANCE: A possible simultaneous involvement of survivin and Hsp72 in tumour invasion and the multistep process of EMT of cutaneous epithelial tumours of dogs is suggested.

Unusual tongue metastasis from lung adenocarcinoma in a cat with feline lung-digit syndrome.

This report describes the pathological findings in a 15-year-old spayed female Domestic Shorthaired cat with a pulmonary adenocarcinoma characterized by feline lung-digit syndrome (FLDS) and unusual tongue metastasis. Felis catus papillomavirus type 3 (FcaPV-3) DNA was amplified from the lingual sample but not from samples of the pulmonary mass or digital or splenic metastatic lesions, indicating the presence of FcaPV-3 in the oral cavity but not suggesting a role for FcaPVs in tumour pathogenesis. FLDS is a clinical entity in which primary lung tumours present because of metastatic digital lesions. In humans, tongue metastasis may be a rare initial presentation of lung cancer, whereas, to the best of our knowledge, tongue metastasis of feline tumours has not been reported. Although lingual metastases are rare, the present findings serve to remind clinicians that metastatic manifestations of primary lung tumours in cats may involve multiple extrapulmonary sites, including the tongue.

Immunohistochemical investigation of cell cycle and apoptosis regulators (survivin, ß-catenin, p53, caspase 3) in canine appendicular osteosarcoma.

BACKGROUND: Osteosarcoma (OSA) represents the most common canine primary bone tumour. Despite several pathways have been investigated so far, few molecules have been identified as prognostic tools or potential therapeutic targets, and there is still the need to find out molecular pathways with specific influence over OSA progression to facilitate earlier prognosis and treatment.Aims of the present study were to evaluate the immunohistochemical pattern and levels of expression of a panel of molecules (survivin, ß-catenin, caspase 3 -inactive and active forms- and p53) involved in cell cycle and apoptosis regulation in canine OSA samples, known to be of interest in the study also of human OSA, and to detect specific relations among them and with histological tumour grade, disease free interval (DFI) and overall survival (OS). RESULTS: Nuclear ß-catenin immunostaining was detected in normal osteoblasts adjacent to the tumour, and in 47% of the cases. Cytoplasmic and/or membranous immunostaining were also observed. Nuclear survivin and p53 positive cells were found in all cases. Moderate/high cytoplasmic ß-catenin expression (≥10% positive cells) was significantly associated with the development of metastasis (P = 0.014); moderate/high nuclear p53 expression (≥10% positive cells) was significantly associated with moderate/high histological grade (P = 0.017) and shorter OS (P = 0.049). Moderate/high nuclear survivin expression (≥15% positive cells) showed a tendency toward a longer OS (P = 0,088). CONCLUSIONS: The present results confirmed p53 as negative prognostic marker, while suggested survivin as a potential positive prognostic indicator, rather than indicative of a poor prognosis. The detection of nuclear ß-catenin immunostaining in normal osteoblasts and the absent/low expression in most of the OSAs, suggested that this pathway could not play a major role in oncogenic transformation of canine osteoblasts. Further studies are needed to confirm these hypotheses.

Nuclear survivin expression as a potentially useful tool for the diagnosis of canine cutaneous sebaceous lesions.

BACKGROUND: Sebaceous glands are specialized cutaneous adnexal glands, which work under constant hormonal control to produce sebum. They can give rise to several proliferative lesions, such as hamartoma, hyperplasia and neoplasms (adenoma, epithelioma and carcinoma). Their nomenclature is currently confusing, both in veterinary and in human medicine, owing to the difficulty of differentiating between some of these lesions. METHODS: The present study used immunohistochemistry to determine the expression levels and patterns of survivin and Ki67 in five samples of normal canine skin and 44 cases of canine cutaneous lesions with sebaceous differentiation (10 hamartomas, nine hyperplasia, eight adenomas, eight epitheliomas and nine carcinomas). RESULTS: In normal glands, survivin, as well as Ki67, was expressed in scattered reserve cells. In hamartomas, survivin was more highly expressed than in normal skin, indicating a possible role of this molecule in the pathogenesis of these congenital lesions. In tumours, a moderate or high level of survivin and Ki67 expression (more than two and four and more than two positive cells, respectively) were significantly correlated with a malignant histotype, infiltrative growth and a moderate or high number of mitoses (more than two). CONCLUSIONS AND CLINICAL IMPORTANCE: The level of survivin expression increased with increasing malignancy, designating survivin as a new diagnostic marker in the assessment of malignancy of sebaceous tumours.

Histological Evaluation of Long-Term Collagen Type I Culture.

Histological approach to long-term culture on collagen type I permits the evaluation of vasculogenic mimicry morphological features and the identification of endothelial-like cell-specific antigens. Here, we show the preparation of collagen type I solution, the embedding and the sections cutting of D17 osteosarcoma cells long-term culture, and then the hematoxylin and eosin (H&E) staining to identify endothelial-like structure. Moreover, we provide the protocols for periodic acid-Schiff (PAS) staining to evidence glycoproteins and CD31 immunohistochemistry to exclude the presence of this endothelial marker, as per definition by vasculogenic mimicry concept. This method allows to consider long-term culture as tissue, promoting the deeper study of vascular-like structures in vitro.

Health and Mortality Monitoring in Threatened Mammals: A First Post Mortem Study of Otters (Lutra lutra L.) in Italy.

Dead specimens provide valuable data for the conservation of threatened species, allowing investigations of mortality, health conditions, and demographic parameters. The Eurasian otter (Lutra lutra) is a semiaquatic carnivore listed as endangered in Italy. In 2009, we started the first post mortem (PM) study of otters in Italy, through collaborative research between mammal ecologists and veterinary pathologists, using standardized protocols. Twenty-eight otters, mostly collected between 2009 and 2017, were examined. Most otters were males (67%), between 1 and 3 years old (64%), and predominantly in good nutritional condition. Adult males were significantly larger than adult females (p < 0.02), as expected for the species, although both sexes appeared to be smaller than otters examined in Central−northern Europe. The youngest sexually mature female was 3 years old. Road traffic collisions were the major cause of death, especially in young individuals, and mainly occurred in autumn−winter, particularly for females. Investigations of the scene of death contributed to revealing factors forcing otters to travel out of the water and move over the road, suggesting appropriate measures to reduce vehicle collision risk. Other causes of death included blunt chest trauma of uncertain origin, dog and conspecific attacks, or diseases of infectious or non-infectious origin, such as ulcerative gastritis, pleuropneumonia and peritonitis. Other diagnosed diseases included lymphoma. Ecto- and endoparasites were rarely detected, although we report the first documentation of heartworm and Ixodes hexagonus infestation in Italian otters. It is important to continue comprehensive, standardized PM investigations of otters in Italy to define baseline health, biometric and demographic parameters, collect biological samples for comparative analyses, and to reduce road-kill mortality. The present study suggests that the timely collection of carcasses and collaborative and coordinated research efforts are essential for obtaining useful data for the conservation of otters.

Strain and Shear-Wave Elastography and Their Relationship to Histopathological Features of Canine Mammary Nodular Lesions.

Mammary gland tumours have a significant impact on the health of dogs, requiring diagnostic tools to support clinicians to develop appropriate therapeutic strategies. Sonoelastography is an emerging technology that is able to define the stiffness of the tissue and has promising applications in the evaluation of mammary gland lesions. In the present study, strain elastography (STE) and shear-wave (SWE) elastography were compared in 38 mammary nodular lesions for their ability to define the histopathological features of canine mammary lesions. Among the techniques, SWE showed better repeatability (intraclass correlation coefficient: 0.876), whereas STE was found to be only acceptable (intraclass correlation coefficient: 0.456). Mammary nodular lesions showed a wide range of tissue stiffening with a similar mean value for STE and SWE in benign (4 ± 0.3 and 115.4 ± 12.6 kPa, respectively) and malignant lesions (3.8 ± 0.1 and 115.5 ± 4.5 kPa, respectively). A significant correlation was found between lesion fibrosis and STE (STE-I: r = 0.513, p < 0.001; STE-R: r = 0.591, p < 0.001) or SWE-S (r = 0.769; p < 0.001). In conclusion, SWE was reliable and correlated with fibrosis and was similar for both benign and malignant lesions, suggesting that other collateral diagnostic techniques should be considered in conjunction with SWE to characterize mammary nodular lesions in dogs.

A Magnetic Resonance-Relaxometry-Based Technique to Identify Blood Products in Brain Parenchyma: An Experimental Study on a Rabbit Model.

Magnetic resonance relaxometry is a quantitative technique that estimates T1/T2 tissue relaxation times. This has been proven to increase MRI diagnostic accuracy of brain disorders in human medicine. However, literature in the veterinary field is scarce. In this work, a T1 and T2-based relaxometry approach has been developed. The aim is to investigate its performance in characterizing subtle brain lesions obtained with autologous blood injections in rabbits. This study was performed with a low-field scanner, typically present in veterinary clinics. The approach consisted of a semi-automatic hierarchical classification of different regions, selected from a T2 map. The classification was driven according to the relaxometry properties extracted from a set of regions selected by the radiologist to compare the suspected lesion with the healthy parenchyma. Histopathological analyses were performed to estimate the performance of the proposed classifier through receiver operating characteristic curve analyses. The classifier resulted in moderate accuracy in terms of lesion characterization.

Reproducibility and Feasibility of Classification and National Guidelines for Histological Diagnosis of Canine Mammary Gland Tumours: A Multi-Institutional Ring Study.

Histological diagnosis of Canine Mammary Tumours (CMTs) provides the basis for proper treatment and follow-up. Nowadays, its accuracy is poorly understood and variable interpretation of histological criteria leads to a lack of standardisation and impossibility to compare studies. This study aimed to quantify the reproducibility of histological diagnosis and grading in CMTs. A blinded ring test on 36 CMTs was performed by 15 veterinary pathologists with different levels of education, after discussion of critical points on the Davis-Thompson Foundation Classification and providing consensus guidelines. Kappa statistics were used to compare the interobserver variability. The overall concordance rate of diagnostic interpretations of WP on identification of hyperplasia-dysplasia/benign/malignant lesions showed a substantial agreement (average k ranging from 0.66 to 0.82, with a k-combined of 0.76). Instead, outcomes on ICD-O-3.2 morphological code /diagnosis of histotype had only a moderate agreement (average k ranging from 0.44 and 0.64, with a k-combined of 0.54). The results demonstrated that standardised classification and consensus guidelines can produce moderate to substantial agreement; however, further efforts are needed to increase this agreement in distinguishing benign versus malignant lesions and in histological grading.

Aural carcinoma with chondroid metaplasia at metastatic sites in a dog.

A case of aural carcinoma with chondroid metaplasia at metastatic foci in an 8-year-old male pug is described. Multiple metastases in both lungs and the right submandibular, parotid, retropharyngeal, cervical and prescapular lymph nodes were detected. Histologically, the skin of the right ear canal appeared to be diffusely infiltrated by cords and nests of neoplastic epithelial cells, showing multifocal contiguity with the overlying hyperplastic squamous epithelium. Most of the carcinomatous cells were arranged in a glandular-like pattern, with formation of lumens containing epithelial cells attached to the peripheral cell layer by elongated intercellular bridges. Scattered foci of keratinization with central accumulations of compact, laminated keratin were also observed, and histochemical stains failed to detect mucinous secretory material. Even though histological and histochemical findings were compatible with a diagnosis of acantholytic squamous cell carcinoma, CAM5.2 immunostaining was detectable in the majority, although not all, neoplastic cells, confirming a diagnosis of poorly differentiated ceruminous gland carcinoma. Pulmonary metastatic nodules revealed multifocal areas of cartilaginous metaplasia with apparent transition of carcinomatous cells to chondroid cells, showing nuclear atypia and focal cytokeratin immunostaining. Carcinomatous cells surrounding chondroid areas also revealed focal vimentin and S100 immunoreactivity. Histological evidence of transition between the two components, as well as the presence of intermediate cells displaying both epithelial and mesenchymal immunohistochemical features, strongly indicated a final diagnosis of carcinosarcoma, in which chondrosarcomatous elements were derived from carcinoma cells.

Oxidative stress in the pathogenesis of canine zinc-responsive dermatosis.

Zinc deficiency causes skin diseases both in humans and in animals. The underlying pathogenic mechanisms remain unclear, but a growing body of evidence indicates a role for zinc in skin protection against free radical-induced oxidative damage. The immunohistochemical expression of heat shock proteins (HSPs; Hsp27, Hsp72, Hsp73 and Hsp90), Cu/Zn superoxide dismutase (SOD), metallothionein (MT), Ki-67 antigen and active caspase-3 were evaluated in normal canine skin and in samples from eight dogs with zinc-responsive dermatosis. All investigated HSPs showed intense cytoplasmic immunostaining in the affected epidermis. Focal nuclear positivity of Hsp72 was also detected in keratinocytes. Although Cu/Zn SOD expression was similar to that observed in normal skin, MT immunoreactivity occurred in both the cytoplasm and the nucleus of basal cells in normal skin but was absent from the affected epidermis. Caspase-3 activation was also absent in the involved epidermis, which revealed a high Ki-67 index (a 3.5- to 9-fold increase compared with normal skin). These results support the hypothesis that cellular response to stress, particularly oxidative stress, is involved in the pathogenesis of skin lesions in canine zinc-responsive dermatosis. The lack of MT immunoreactivity in the affected epidermis may be indicative of low zinc levels, thus resulting in vulnerability to oxidative damage. In contrast, high expression levels of HSPs in skin during zinc deficiency may confer protection against a variety of dangerous stimuli, contributing to inhibition of apoptosis and to cell cycle regulation of proliferating keratinocytes.

An Update on Molecular Pathways Regulating Vasculogenic Mimicry in Human Osteosarcoma and Their Role in Canine Oncology.

Canine tumors are valuable comparative models for human counterparts, especially to explore novel biomarkers and to understand pathways and processes involved in metastasis. Vasculogenic mimicry (VM) is a unique property of malignant cancer cells which promote metastasis. Thus, it represents an opportunity to investigate both the molecular mechanisms and the therapeutic targets of a crucial phenotypic malignant switch. Although this biological process has been largely investigated in different human cancer types, including osteosarcoma, it is still largely unknown in veterinary pathology, where it has been mainly explored in canine mammary tumors. The presence of VM in human osteosarcoma is associated with poor clinical outcome, reduced patient survival, and increased risk of metastasis and it shares the main pathways involved in other type of human tumors. This review illustrates the main findings concerning the VM process in human osteosarcoma, search for the related current knowledge in canine pathology and oncology, and potential involvement of multiple pathways in VM formation, in order to provide a basis for future investigations on VM in canine tumors.

Hypertrophic gastropathy associated with gastric sarcoma in a dog.

A 14-y-old spayed female Labrador Retriever was presented with an 8-mo history of chronic vomiting. Abdominal ultrasound and gastrointestinal endoscopy revealed a mass protruding into the gastric lumen, with cytologic features suggestive of sarcoma. A partial gastrectomy was performed; the gastric body and antrum were thickened, with a cerebriform appearance of the mucosal surface. Histologic examination revealed a submucosal neoplastic proliferation of fusiform cells variably arranged in irregular bundles and scattered whorls. Fusiform cells strongly reacted to antibodies against vimentin, S100, and neuron-specific enolase; glial fibrillary acidic protein was moderately and multifocally expressed. Pancytokeratin, KIT, α-smooth muscle actin, and desmin were nonreactive. Histologic and immunohistochemical findings suggested a diagnosis of gastric sarcoma with features referable to a non-GIST (gastrointestinal stromal tumor), non-smooth muscle NIMT (non-angiogenic, non-lymphogenic intestinal mesenchymal tumor). The overlying gastric mucosa was thickened by elongated and dilated gastric glands, predominantly lined by intensely periodic acid-Schiff-stained mucous cells. This altered mucosal architecture was suggestive of Ménétrier-like disease. Although this disease has been hypothesized to predispose to gastric adenocarcinoma in dogs, an association with gastric sarcoma has not been documented previously in the veterinary literature, to our knowledge.