Establishment and characterization of a novel cell line and xenotransplant mouse model derived from feline colorectal adenocarcinoma.

Colorectal adenocarcinoma is an aggressive malignant tumor in cats that frequently metastasizes to the lymph nodes and/or distant organs. However, research on feline colorectal adenocarcinoma is limited, and experimental models have not been established. A novel cell line, FeLeco-G7, was established from the lymph node of a 12-year-old spayed female Maine Coon cat with metastatic colorectal adenocarcinoma. FeLeco-G7 cells were polygonal with abundant cytoplasm and adherent growth. The population-doubling time was approximately 28.3 hours, and the mean number of chromosomes was 37.6±0.1 per cell (ranging between 32 and 41). Consistent with the original tumor, FeLeco-G7 cells were immunopositive for cytokeratin (CK) 20 and CDX2, and immunonegative for CD10 and CK7. Nuclear accumulation of ß-catenin was rarely observed. Mutation analysis suggested TP53 gene alterations. A subcutaneous injection of FeLeco-G7 cells into immunodeficient mice resulted in the formation of a mass at the injection site without the development of metastatic lesions. An orthotopic (intrarectal) transplantation of FeLeco-G7 cells caused cachexia and diffuse involvement of the rectal mucosa in one of the 3 mice and the formation of masses around the rectum in the other 2 mice. Metastases to the regional lymph nodes and lungs were detected in three of the 3 and one of the 3 mice, respectively. The histological findings and immunohistochemical features of these masses were similar to those of the original tumor. These results suggest that FeLeco-G7 cells and the orthotopically transplanted mouse model are valuable tools for further molecular and therapeutic research on feline colorectal adenocarcinoma.

Transcriptomic analysis reveals immune infiltration status and potential biomarkers of canine colorectal cancer.

Colorectal cancer (CRC) in dogs has been shown to have similar molecular characteristics to human colorectal cancer. Although researchers have explored the pathogenesis and immune status of human CRC, the canine CRC has been far less studied. As a result, we analyzed canine colorectal tumors and normal canine intestinal samples by Gene Set Enrichment Analysis (GSEA) and found significant enrichment of immune-related pathways, including the TNF-α signaling pathway and IL6-STAT3 signaling pathway. In addition, the differential infiltration of naive B cells and regulatory T cells suggested that canine CRC was in a state of immunosuppression. Weighted gene co-expression network analysis (WGCNA) revealed the gene modules that contribute to differences in regulatory T cell inetfiltration, Further cross-validation of canine and human CRC differential genes obtained three core genes that are both species-conserved and differentially expressed, CD44, NAT10, and ETV4, of which NAT10 and ETV4 have been little studied in the immune status of colorectal cancer. Our findings may have implications for the pathogenesis and progression of CRC in dogs and could be a new potential therapeutic target for CMT and provide a bioinformatics foundation for later clinical experiment validation.

Application of endoscopic ultrasound to the descending colon and rectum in normal dogs.

Endoscopic ultrasound (EUS) is a medical procedure in which endoscopy is combined with ultrasonography (US) to compensate for problems associated with the transabdominal US such as large penetration depths, presence of intestinal gas, and acoustic shadowing. This prospective, method comparison, pilot study was performed to assess the feasibility of applying EUS in the colorectal region and to describe the typical EUS features of the descending colon and rectum in healthy dogs. Transabdominal US and EUS with or without the hydrosonography were applied to the descending colon and rectum in 10 clinically healthy Beagle dogs and wall thickness, visibility of the wall layers, and conspicuity of the mucosal and serosal surfaces of the intestinal wall were assessed. Endoscopic ultrasound enabled circumferential evaluation of the colorectal wall and provided better visibility of the wall layers and conspicuity of the mucosal and serosal surfaces without degradation of the image, even in the far-field portion of the colorectal wall, compared to US. Moreover, EUS provided the adequate image quality of the rectum, which was difficult to evaluate with US due to deep scan depth and acoustic shadowing by the pelvis. Meanwhile, the application of hydrosonography to EUS deteriorated the visibility of the wall layers and conspicuity of the intestinal wall. The results of this study demonstrate the feasibility of EUS to assess the colorectal region and its potential application for the evaluation of rectal masses or intrapelvic lesions that are inaccessible by the transabdominal US in dogs.

Relationship of microsatellite instability to mismatch repair deficiency in malignant tumors of dogs.

BACKGROUND: Microsatellite instability (MSI) is a type of genomic instability caused by mismatch repair deficiency (dMMR) in tumors. Studies on dMMR/MSI are limited, and the relationship between dMMR and MSI is unknown in tumors of dogs. OBJECTIVES: We aimed to identify the frequency of dMMR/MSI by tumor type and evaluate the relationship between dMMR and MSI in tumors of dogs. ANIMALS: In total, 101 dogs with 11 types of malignant tumors were included. METHODS: We extracted DNA from fresh normal and tumor tissues. Twelve microsatellite loci from both normal and tumor DNA were amplified by PCR and detected by capillary electrophoresis. Each microsatellite (MS) was defined as MSI if a difference in product size between the tumor and normal DNA was detected. The dMMR was evaluated by immunohistochemistry with formalin-fixed paraffin-embedded tumor tissues. Next, we confirmed whether dMMR induces MSI by serial passaging of MMR gene knockout cell lines for 3 months. RESULTS: Microsatellite instability was detected frequently in oral malignant melanoma. The number of MSI-positive markers was higher in cases with dMMR than in those with proficient MMR (P < .0001). Statistical analysis indicated that the occurrence of MSI in FH2305 might have relevance to dMMR. Furthermore, MSI occurred in dMMR cell lines 3 months after passaging. CONCLUSIONS AND CLINICAL IMPORTANCE: Microsatellite instability and dMMR more frequently were found in oral malignant melanoma than in other tumors, and dMMR has relevance to MSI in both clinical cases and cell lines.

Molecular epidemiological study of germline APC variant associated with hereditary gastrointestinal polyposis in dogs: current frequency in Jack Russell Terriers in Japan and breed distribution.

BACKGROUND: Cases of gastrointestinal (GI) neoplastic polyps in Jack Russell Terriers (JRTs) have increased in Japan since the late 2000s. We recently demonstrated that JRTs with GI polyps heterozygously harbor an identical germline variant in the adenomatous polyposis coli (APC) gene, c.[462_463delinsTT]; therefore, this is an autosomal dominant hereditary disease. We conducted a molecular epidemiological study to explore the current frequency of the APC variant in JRTs in Japan and the breed distribution of this disease. RESULTS: Peripheral blood samples from 792 JRTs were collected at 93 veterinary hospitals in Japan in 2020. Using an established polymerase chain reaction-restriction fragment length polymorphism assay, the germline APC variant was detected in 15 JRTs, with an overall frequency of 1.89%. The frequency was not significantly different for sex, age, and coat type criteria. Notably, the variant carriers had a current or previous history of GI neoplastic polyps, providing further evidence of the association of the germline APC variant with GI polyposis. Pedigree analysis of carrier dogs revealed that the germline APC variant was no longer confined to a few specific families but was widely spread among JRTs in Japan. Furthermore, some ancestors of the carriers were from Australia or New Zealand, suggesting the possible presence of carriers in countries other than Japan. Next, we retrospectively investigated the germline APC variant status of dogs with GI epithelial tumors using genomic DNA samples extracted from archived pathological specimens (28 purebred dogs of 14 breeds and four mixed-breed dog), as well as those stored in a canine genome bank (38 dogs of 18 breeds and a mixed-breed dogs). In total, 66 purebred dogs of 25 breeds, including another four JRTs, and five mixed-breed dogs were examined. While three variant carriers were found in JRTs, the germline APC variant was not detected in any of the other breeds. CONCLUSION: The current frequency of the germline APC variant was approximately 2% in JRTs in Japan and the frequency remained roughly flat during the last 15 years. In addition, hereditary GI polyposis associated with the variant was virtually specific to JRTs.

Serum vascular endothelial growth factor in dogs with various proliferative diseases.

Angiogenesis plays an important role in the proliferation and metastasis mechanisms of malignant tumors. Vascular endothelial growth factor (VEGF), a group of cytokines that contribute to angiogenesis and vasculogenesis. This study aimed to investigate the serum VEGF-A concentrations in dogs with various proliferative diseases. A total of 202 dogs that were histopathologically diagnosed with proliferative diseases were included in the study. Serum VEGF-A concentrations were measured using enzyme-linked immunosorbent assay. Median serum VEGF-A concentrations in dogs were as follows: healthy dogs, 4 pg/ml [0-21 pg/ml]; hepatocellular carcinoma, 30 pg/ml [0-158 pg/ml, P=<0.001]; hepatocellular adenoma, 32 pg/ml [0-49 pg/ml, P=0.003]; hepatic nodular hyperplasia, 18 pg/ml [0-51 pg/ml, P=0.595]; adrenal pheochromocytoma, 32 pg/ml [0-187 pg/ml, P=<0.001]; adrenocortical carcinoma, 32 pg/ml [3-161 pg/ml, P=0.002]; adrenocortical adenoma, 27 pg/ml [0-106 pg/ml, P=0.005]; colorectal adenocarcinoma, 36 pg/ml [0-75 pg/ml, P=0.002]; colorectal adenoma, 43 pg/ml [0-48 pg/ml, P=0.144]; inflammatory colorectal polyps, 37 pg/ml [0-111 pg/ml, P=<0.001]; pulmonary adenocarcinoma, 35 pg/ml [4-107 pg/ml, P=0.002]; pulmonary histiocytic sarcoma, 35 pg/ml [0-131 pg/ml, P=0.016]; and follicular thyroid carcinoma, 35 pg/ml [0-106 pg/ml, P=0.009]. The serum VEGF-A concentrations were significantly higher in dogs with neoplastic lesions compared to healthy dogs, except for colorectal adenoma. High serum VEGF-A concentrations were observed in dogs with proliferative diseases. The present study suggests that angiogenesis-inhibiting therapy, which targets VEGF-A, may be useful for canine neoplastic diseases.

Sox9, Hopx, and survivin and tuft cell marker DCLK1 expression in normal canine intestine and in intestinal adenoma and adenocarcinoma.

Self-renewal of the intestinal epithelium originates from stem cells located at the crypt base. Upregulation of various stem cell markers in intestinal epithelial neoplasms indicates a potential role of stem cells in tumorigenesis. In this study, the immunoreactivity of potential intestinal stem cell markers (Sry box transcription factor 9 [Sox9], homeodomain-only protein [Hopx], survivin) and tuft cell marker doublecortin-like kinase 1 (DCLK1) in normal canine intestine and intestinal epithelial neoplasms was investigated. Formalin-fixed paraffin-embedded (FFPE) small and large intestine as well as intestinal neoplasms (55 colorectal adenomas [CRAs], 17 small intestinal adenocarcinomas [SICs], and 12 colorectal adenocarcinomas [CRCs]) were analyzed immunohistologically. Potential stem cell markers Sox9, Hopx, and survivin were detected in the crypts of normal canine small and large intestine. DCLK1+ tuft cells were present in decreasing numbers along the crypt-villus axis of the jejunum and rarely detectable in large intestine. In canine intestinal epithelial tumors, nuclear Sox9 immunoreactivity was detectable in 84.9% (CRA), 80% (CRC), and 77% of epithelial neoplastic cells (SIC). Hopx and survivin were expressed within cytoplasm and nuclei of neoplastic cells in benign and malignant tumors. DCLK1 showed a cytoplasmic reaction within neoplastic cells. The combined score of Hopx, DCLK1, and survivin varied among the examined cases. Overall, malignant tumors showed lower DCLK1 scores but higher Hopx scores in comparison with benign tumors. For survivin, no differences were detectable. In conclusion, stem cell markers Sox9, Hopx, and survivin were detectable at the crypt base and the immunoreactivity of Sox9, DCLK1, survivin, and Hopx was increased in canine intestinal adenomas and adenocarcinomas compared with normal mucosa.

Assessment of colorectal anastomosis perfusion with confocal laser endomicroscopy − an experimental study

Introduction: Early diagnosis of complicated healing of colorectal anastomosis can increase the chance for salvage surgery and thus reduce overall morbidity. Confocal laser endomicroscopy (CLE) enables in vivo assessment of tissue perfusion without disturbing its integrity. This experimental study evaluates the potential of CLE for postoperative monitoring of colorectal anastomosis. Methods: A hand-sewn colorectal anastomosis was performed in 9 pigs. The animals were subsequently divided into groups with normal (N=3) and ischemic anastomosis (N=6). Microscopic signs of hypoperfusion were evaluated postoperatively at regular intervals using CLE. Results: Uneven saturation of the images was evident in the group with ischemic anastomosis. The epithelium had inhomogeneous edges and more numerous crypt branching was visible. Tissue oedema quantified as the number of crypts per visual field was already more extensive at the first measurement after induction of ischemia. There was also a significant difference between the values measured before and 10 minutes after ischemia ­ 8.7±1.9 vs. 6.0±1.1 (p=0.013). Conclusion: Postoperative monitoring of the colorectal anastomosis using CLE enables prompt detection of perfusion disorders.

Mismatch repair deficiency in canine neoplasms.

The DNA mismatch repair (MMR) system preserves genomic stability by identifying and repairing mismatched nucleotides in the DNA replication process. The dysfunction of the MMR system, also known as mismatch repair deficiency (dMMR), is implicated as a predictive biomarker for the efficacy of immune checkpoint blockade therapy regardless of the tumor type in humans. This study aimed to evaluate the immunolabeling of MMR proteins in canine tumors and to identify the types of tumors having dMMR. First, we performed immunohistochemistry in 8 different canine tumors (oral malignant melanoma, high-to-intermediate grade lymphoma, mast cell tumor, malignant mammary gland tumor, urothelial carcinoma, hepatocellular carcinoma, osteosarcoma, and hemangiosarcoma) with 15 samples each to analyze the immunolabeling of canine mismatch repair proteins (MSH2, MSH6, and MLH1) using anti-human monoclonal antibodies. We found that more than half of canine oral malignant melanoma (60%) and hepatocellular carcinoma (53%) samples and fewer of the other canine tumors had loss of immunolabeling in ≥1 MMR protein (ie, evidence of defective MMR proteins, based on the definition of dMMR in the humans). Antibodies against human MSH2, MSH6, and MLH1 were cross-reactive with the corresponding canine protein as confirmed using MMR gene knockout canine cell lines. Further studies are required to investigate the clinical outcomes in canine spontaneous tumors with dMMR to determine the potential for immune checkpoint blockade therapy for these tumor types.

Immunohistochemical expression of ß-catenin, Ki67, CD3 and CD18 in canine colorectal adenomas and adenocarcinomas.

BACKGROUND: Inflammation is believed to influence human colorectal carcinogenesis and may have an impact on prognosis and survival. The mucosal immunophenotype in dogs with colorectal cancer is poorly described. The aim of this study was to investigate whether the density, distribution and grade of tumor-infiltrating immune cells (TIIs) are different in normal colonic tissue vs benign stages (adenomas) and malignant stages (adenocarcinomas) of canine colorectal carcinogenesis, and thus, whether they can be considered as prognostic factors in dogs. This retrospective case-control study was performed on formalin-fixed, paraffin-embedded tissue samples from dogs with histologically confirmed colorectal adenoma (n = 18) and adenocarcinoma (n = 13) collected from archived samples. The samples had been collected by colonoscopy, surgery or during postmortem examination. Healthy colonic tissue obtained post mortem from dogs euthanized for reasons not involving the gastrointestinal tract served as control tissue (n = 9). RESULTS: The tumor samples had significantly lower numbers of CD3+ T-cells in the epithelium compared to controls (adenocarcinoma vs control, Kruskal-Wallis test, p = 0.0004, and adenoma vs control, p = 0.002). Adenomas had a significantly lower number of CD18+ cells in the lamina propria, compared to control samples (Kruskal-Wallis test, p = 0.008). Colonic samples from control dogs had uniform staining of ß-catenin along the cell membrane of epithelial cells. Compared to normal colonic cells, the expression levels of cytoplasmic ß-catenin were significantly higher in adenomas and adenocarcinomas (adenoma vs control Kruskal-Wallis test, p = 0.004, and adenocarcinoma vs control, p = 0.002). None of the control samples showed positive staining of ß-catenin in the nucleus of colonic cells. In contrast, adenocarcinomas and adenomas showed moderate to strong staining of the cell nucleus. The nuclear ß-catenin expression (signal strength and distribution) was significantly higher in adenomas compared to adenocarcinomas (Kruskal-Wallis test, p < 0.05). CONCLUSIONS: ß-catenin and Ki67 were not useful markers for demonstrating tumor progression from adenomas to adenocarcinomas. The lower presence of CD18 and CD3+ cells in colorectal tumors compared to controls indicates a reduced presence of histiocytes and T-cells, which may have implications for the pathogenesis and progression of colorectal cancer in dogs.

Canine Tonsillar Polyps: Characteristics, Classification, and Review of the Pathogenesis.

Canine tonsillar polyps are uncommon. We describe 14 tonsillar polyps in dogs and review their classification and pathogenesis. All dogs were adult (3-13 years old). Females (10/14) were more affected than males (4/14). Most of the lesions were asymptomatic (10/14). All lesions were unilateral, pedunculated (9/14), or sessile (5/14), with a smooth (12/14) or papillary/verrucous surface (2/14). Histologically, polyps consisted of benign proliferation of lymphatic vessels, blood vessels, fibrous tissue, and lymphoid tissue in variable proportions, with occasional adipose tissue (4/14). According to the main stromal components, polyps were categorized as lymphangiomatous (5/14), lymphangiolipomatous (2/14), lymphangiofibromatous (2/14), angiofibromatous (1/14), angiofibrolipomatous (1/14), lymphoid (2/14), and myxomatous (1/14). As the pathogenesis of these polyps remains unclear, we propose to replace the term inflammatory tonsillar polyp by a morphological diagnosis based on the stromal characteristics of the lesions. Simple surgical excision was curative in the 9 cases with available follow-up information.

Histological Classification and Immunohistochemical Study of Feline Colorectal Epithelial Tumors.

Among 113 feline gastrointestinal epithelial tumors diagnosed between 2006 and 2019, 78 (69%) were detected in the colorectum. Fifty colorectal tumors were selected for further pathological evaluations, of which 9 (18%) were histopathologically diagnosed as adenomas and 41 (82%) as carcinoma. The carcinomas included 33 tubular adenocarcinomas (TAC), 5 tubulovillous adenocarcinomas (TVAC), 2 mucinous adenocarcinomas, and 1 undifferentiated carcinoma. Histopathologically, TAC frequently showed vascular invasion (17/33 cases, 52%). In TAC cases, serosal infiltration (13/15 cases, 87%) and lymph node metastasis (8/9 cases, 89%) were common in bowel resection and lymphadenectomy samples, respectively. Immunohistochemically, the tumor cells of most cases were positive for cytokeratin (CK) 20 (50/50 cases, 100%) and CDX2 (48/50 cases, 96%). Focal immunopositivity for CD10 (11/50 cases, 22%) and CK7 (15/50 cases, 30%) was observed irrespective of the histological subtype. Only a few cases showed diffuse nuclear accumulation of ß-catenin (2/50 cases, 4%) and p53 (5/50 cases, 10%). A lack of tubule formation, female sex, and low CDX2 labeling were statistically associated with carcinoma compared to adenoma (ρ = 0.615, P < .001; ρ = 0.279, P = .050; and ρ = -0.265, P = .063, respectively). Other features, including mucin profiles, Ki67 labeling index, and accumulation of ß-catenin and p53, were not associated with malignancy. A sequence analysis revealed KRAS mutations in 3/7 TAC cases. These results suggest that KRAS mutations-rather than excessive Wnt/ß-catenin signaling and the inactivation of TP53-contribute to the tumorigenesis of feline colorectal carcinoma.

Colorectal basidiobolomycosis in a dog.

A 7-year-old castrated male French Bulldog was examined for chronic large intestinal enteropathy. A colonic mass and thickened rectal mucosa were identified, and histopathologic examination of endoscopic biopsy specimens disclosed eosinophilic proctitis with large (5-20 µm), irregularly shaped, pauciseptate hyphae that were Gomori methenamine silver and periodic acid-Schiff positive. Amplification and sequencing of ribosomal DNA extracted from paraffin-embedded tissues yielded a sequence with 97% identity to GenBank sequences for Basidiobolus ranarum. After itraconazole, terbinafine, and prednisone administration, clinical signs resolved rapidly, and sonographic lesions were largely absent after 6 weeks. Treatment was discontinued by the owner 15 weeks after diagnosis. Three weeks later, the dog collapsed acutely and was euthanized. Necropsy identified metastatic islet cell carcinoma and grossly unremarkable colorectal tissues. However, histopathology of the rectum disclosed multifocal submucosal granulomas with intralesional hyphae morphologically similar to those previously observed. This report is the first to describe medical treatment of gastrointestinal basidiobolomycosis in a dog.

Activities of matrix metalloproteinase-2, matrix metalloproteinase-9, and serine proteases in samples of the colorectal mucosa of Miniature Dachshunds with inflammatory colorectal polyps.

OBJECTIVE: To investigate the activities of gelatinases (matrix metalloproteinase [MMP]-2 and MMP-9) and serine proteases in the colorectal mucosa of Miniature Dachshunds (MDs) with inflammatory colorectal polyps (ICRPs). ANIMALS: 15 MDs with ICRPs and 5 dogs with non-ICRP-related large bowel diarrhea (controls). PROCEDURES: Zymographic methods were used to evaluate the activities of MMP-2, MMP-9, latent forms of MMP-2 and MMP-9 (pro-MMP-2 and pro-MMP-9), and serine proteases in inflamed and noninflamed tissue samples from MDs with ICRPs and in noninflamed tissue samples from control dogs. The associations of serine protease activities with MMP-2 or MMP-9 activity were also analyzed. RESULTS: Activities of pro-MMP-2 and pro-MMP-9 were detected in most tissue samples, regardless of the tissue type, whereas activities of MMP-2 and MMP-9 were not detected in control tissue samples. In the inflamed tissue samples from MDs with ICRPs, the activities of MMP-2, pro-MMP-9, and MMP-9 were significantly higher than those in the noninflamed tissue samples from those dogs. Serine protease activities were significantly higher in the inflamed and noninflamed tissue samples from MDs with ICRP, compared with findings for control tissue samples. A weak correlation was detected between serine protease activities and MMP-9 activity. CONCLUSIONS AND CLINICAL RELEVANCE: Study results suggested that gelatinase and serine protease activities are upregulated in the colorectal mucosa of MDs with ICRPs, possibly contributing to the pathogenesis of this disease through the functions of these enzymes in degradation of extracellular matrix and promotion of inflammatory cell migration and inflammatory responses.

Obturator-Assisted Prolapse for Access to and Sampling of Colorectal Masses in Seven Dogs.

The gold standard for diagnosis of colorectal masses is surgical biopsy; however, this is not always logistically or economically feasible. The authors present an alternative to established flexible and rigid endoscopic approaches when case limitations require such an approach. In seven dogs, after the identification of a mass on physical exam and computed tomographic evaluation, the colorectum was accessed using obturator-assisted prolapse to isolate discrete masses and perform shielded sampling via core needle biopsy. Histopathologic diagnosis was adequate for treatment planning in all dogs. No major complications were recorded 65-475 days after the procedure. This technique may be useful when traditional endoscopy and surgery for biopsy of colorectal masses is unavailable.

cGAMP inhibits tumor growth in colorectal cancer metastasis through the STING/STAT3 axis in a zebrafish xenograft model.

The leading cause of mortality due to colorectal cancer (CRC) is highly associated with the development of liver metastases. Recently, we described cGAMP that is closely related to the metastatic state wherein the progress of metastatic tumors is associated with favorable outcomes in a zebrafish xenograft model. cGAMP was administered and the expression levels of type-I interferons were induced amongst tumor tissues to illuminate the overall measure of the induced STING/STAT3 axis in colorectal liver metastases. Furthermore, cGAMP-STING dependent STAT3 activation resulted in the inhibition of tumor cell proliferation, viability, and invasion in vitro. The subtotal reduction in tumor growth attributed to a large number of infiltrating inflammatory cells in vivo. We showed that cGAMP inhibited migration through angiogenesis by up-regulating IL-2, TNF-α, and IFN-γ, whereas STAT3 down-regulation inhibited CXCL8, BCL-2, and VEGFA expression. The importance of cGAMP in inhibiting the invasion front of CRC confirmed that the cGAMP dependent activation of STING/STAT3 axis played a key role in the inhibition of tumor progression.

Primary Colorectal Follicular Lymphoma in 3 Dogs.

Primary colorectal follicular lymphomas are rare indolent lymphoid neoplasms in humans that have not been reported in dogs. We describe 3 cases of primary colorectal follicular lymphoma in dogs with histologic and immunohistochemical features similar to their human counterpart. Initial clinical signs in all dogs included tenesmus, hematochezia, and a palpable rectal mass. Two dogs were castrated males and 1 an intact female, between 9 months and 2 years of age, and of varied breeds. All 3 cases of colorectal follicular lymphoma were characterized by proliferation of follicular germinal centers with no polarity or mantle zone and were composed of centrocytes admixed with fewer centroblasts. By immunohistochemistry, lymphoid cells expressed CD20, BCL2, and BCL6 and lacked expression of CD3, CD5, and cyclin D1. Polymerase chain reaction for rearrangements of the immunoglobulin heavy chain confirmed a monoclonal population in all cases. In 2 of the 3 cases, a solitary nodular colorectal mass was excised and appeared curative; however, the third case had multiple colorectal masses and the animal developed multicentric lymphoma. This case series immunohistochemically characterizes and distinguishes colorectal follicular lymphoma from atypical lymphoid hyperplasia.

Histopathologic Features of Colorectal Adenoma and Adenocarcinoma Developing Within Inflammatory Polyps in Miniature Dachshunds.

Biopsy samples of colorectal polyps were collected and examined from 67 Miniature Dachshund dogs (including 35 cases with an additional biopsy). Histopathologic diagnoses of the initial biopsy samples were "inflammatory polyp" in 52 cases (78%), "adenoma" in 10 cases (15%), and "adenocarcinoma" in 5 cases (8%). Eight of 10 cases (80%) diagnosed as adenoma also had inflammatory polyp lesions in the same specimen. A second biopsy was performed in 25 cases (48%) initially diagnosed with inflammatory polyp. Pathologic diagnoses for the second biopsy were inflammatory polyp in 11 cases (44%), adenoma in 9 cases (36%), and adenocarcinoma in 5 cases (20%). The number of beta-catenin-positive nuclei in epithelial cells was significantly higher in adenoma (46%) and adenocarcinoma (75%) as compared with inflammatory polyp (6%). Normal epithelial cells and hyperplastic goblet cells in inflammatory polyps showed homogeneous positive cytoplasmic immunoreactivity for adenomatous polyposis coli (APC) antigen. However, APC expression was decreased in areas of intense nuclear beta-catenin expression in adenoma and adenocarcinoma lesions. Foci of cytokeratin 5/6-positive squamous cell-like neoplastic cells showed intense beta-catenin nuclear expression that was similar to squamous morules described in human colorectal tumors. The results of the present study suggest that the inflammatory polyp in Miniature Dachshunds is a progressive disease that may develop into adenoma and/or adenocarcinoma. In addition, immunohistochemical findings suggest that aberrations of APC and beta-catenin expression may be involved in tumor development within the inflammatory polyp lesions.

Adenocarcinoma of the posterior segment of the gastrointestinal tract in dogs - clinical, endoscopic, histopathological and immunohistochemical findings.

Of all the tumours in dogs, three percent are located in the intestines, and 36-60% of those tumours affect the large intestine. Adenocarcinomas of the intestines account for 20-35% of the gastrointestinal tumours and for almost 60% of the large intestine tumours. The aim of the study was to analyze clinical disorders and endoscopic, histopathological and immunohistochemical changes in colorectal adenocarcinomas in dogs with the use of the E-cadherin, ß-catenin, cytokeratin 20 (CK20), Ki-67 and minichromosome maintenance 3 (MCM-3). The study comprised 11 dogs of both genders and of different breeds diagnosed with adenocarcinoma of the large intestine. They were from 4 to 11 years old. The large intestine adenocarcinoma was diagnosed in all the patients. 72.7% cases were diagnosed with a rectal adenocarcinoma, and 27.3% were found to have a colonic adenocarcinoma. All the studied proteins were expressed at different levels and, together with the histological findings, indicated different levels of malignancy (G). The statistical analysis revealed no statistically significant differences between the expression of E-cadherin and ß-catenin in the studied tissues (p=0.79) and between the expression of Ki-67 andMCM-3 (p=0.39). A strong positive correlation was found between the expression of E-cadherin and ß-catenin (r=0.86; p<0.05). The diagnosis of adenocarcinomas of the large intestine may be facilitated by the introduction of immunohistochemical studies using appropriate cell markers. They may also aid in the accurate evaluation of the biological character of the tumours, their origin, the connections between tumour cells and the mitotic index. That, in turn, may help determine the malignancy and the choice of treatment.

Ki-67 protein expression and tumor associated inflammatory cells (macrophages and mast cells) in canine colorectal carcinoma.

BACKGROUND: Ki67 index, tumor associated macrophages (TAMs) and mast cells (MCs) are associated with malignancies in animal and human neoplasms including colorectal carcinomas (CRC). This has not been assessed in canine CRC. Given similar genetic abnormalities between human and canine CRC, we assessed Ki-67 and mitotic indices, TAMs and MC count (MCC) in canine CRC (n = 17). TAMs and MCC were compared with those in adenomas (n = 13) and control (n = 9). RESULTS: Ki-67 index in CRC (17.13 ± 11.50) was strongly correlated (r = 0.98, p < 0.05) with mitotic index (3.52 ± 1.80). MCC was higher (p < 0.05) in CRC (6.30 ± 3.98) than in adenomas (0.78 ± 0.77) and control (0.35 ± 0.33). The results suggest that Ki-67 index and MCC are associated with malignancy in canine CRC. Higher average TAMs were counted in adenomas (21.30 ± 20.70) and in CRC (11.00 ± 9.82) than in the control (7.69 ± 7.26), although the differences were not significant (p > 0.05). CONCLUSION: Ki-67 index, TAMs and MCC in canine CRC were recorded for the first time in this study. Ki-67 index and MCC are associated with malignancy in canine CRC. Quantitative assessment of MCs and Ki-67 coupled with mitotic index and other clinical parameters may help in evaluating malignancy in canine CRC. TAMs likely play a role in the development of canine colorectal tumors. Further studies to determine the clinical significance of these parameters for prognostic, chemo-preventive and chemotherapeutic purposes in canine colorectal tumors are recommended.