Abstract. Mast cell tumors (MCTs) of gastrointestinal origin that had been surgically removed from 39 dogs were examined to evaluate their pathologic features. Miniature breeds, especially Maltese, were most frequently affected. The average age of affected dogs was 9.7 Ϯ 2.6 years. No sex difference was apparent. The most frequently affected sites were in the upper digestive tract, and the prognosis was very poor. Grossly, the gastrointestinal wall was prominently thickened, and the lumen of the affected gut was usually narrowed. Microscopically, there was diffuse transmural invasion of round to pleomorphic tumor cells. Tumor cells had moderate to abundant cytoplasm, round to ovoid nuclei with scattered chromatin, and mitotic figures. Fibrous stroma was observed in about half of the tumors. There was variable infiltration of eosinophils. In all tumors, cytoplasmic granules showed weak metachromasia, but the number of granules was very small. Immunohistochemical staining for c-kit and mast cell tryptase was positive in 77% and 62% of tumors, respectively. All tumors were positive for at least two of these markers. Immunohistochemical staining for p53 was positive in 13% of the tumors. Reactivity for staining markers and p53 was unrelated to cell pleomorphism, vessel invasion, or survival time. Gastrointestinal MCTs have histologic and immunohistochemical features completely different from those of other primary or metastatic gastrointestinal tumors. The combination of immunostaining for mast cell tryptase and c-kit and histochemical staining for metachromasia appears to be a powerful tool for the diagnosis of gastrointestinal MCTs.

With the aims of sharing information about the technical aspects of immunohistochemistry (IHC) and making it possible to make a suitable choice of antibody for histopathological examination, this technical report describes the results of a questionnaire administered during the period of 2014 to 2015 to members of the Conference on Experimental Animal Histopathology. It also describes the immunological properties of primary antibodies (clone, supplier, catalog number, species reactivity, etc.) and the IHC staining conditions (fixing solution, fixing time, embedding, antigen retrieval method, antibody dilution, incubation time, incubation temperature, positive control tissue, secondary antibody information, etc.) for a total number of 733 primary antibodies (425 kinds of primary antibody).

Abstract. We occasionally encounter feline cervical or mesenteric lesions diagnosed histopathologically as abscess or inflammatory granulation tissue with eosinophil infiltration. Gram-positive cocci accompany the lesions. In the present study, such lesions obtained from 27 cats were examined to evaluate the histopathologic features and the nature of the causative bacteria. The average age was 7.3 Ϯ 3.5 years. No sex predilection was observed. Most frequent locations of the lesions included the abdominal cavity with/without mesenteric lymph nodes (11/ 27, 41%) and subcutaneous tissue or lymph nodes of the neck (9/27, 33%). Common clinical presentation was a localized mass. Grossly, the lesions contained abscesses in the center and were surrounded by fibrous tissue. Microscopically, the necrotic zone contained bacterial colonies. Large numbers of eosinophils and macrophages infiltrated the area surrounding the necrotic tissue. The surrounding connective fiber-rich granulation tissue demarcated the eosinophilic abscess. The bacteria were Gram-positive cocci in 23 of the 27 cats and were positive for anti-staphylococcus antiserum in 19 of the 23 cats. In 15 out of 17 lesions, the colonies expressed immunoreactivity to penicillin-binding protein 2Ј, which is a drug-resistance gene product of methicillin-resistant Staphylococcus (MRS) species. These findings suggest strongly that MRS causes this type of infectious lesion.

Male rats of WBN/Kob strain are one of the diabetic model animals and develop long-lasting diabetic symptoms and some complications from about 40 weeks of age without any treatment. A single intravenous dose of alloxan, a non-genotoxic diabetogenic chemical, frequently induced proliferative lesions of squamous epithelium in tongue, esophagus and forestomach of male and female WBN/Kob rats, and hastened the onset and acceleration of diabetic conditions. Histopathologically, proliferative changes of squamous cell of forestomach varied with the severity of hyperplasia in alloxan-treated rats (100% of 31 males and 94.1% of 17 females) and progressed to SCC in approximately 20% of all rats. Metastasis to regional lymph nodes was also observed in two cases. Proliferative changes were most severe in the forestomach and were constantly accompanied with chronic suppurative inflammation of the mucosal epithelium with infection of filamentous fungi and/or bacterial colonies. In contrast, forestomach of the spontaneously diabetic male rats showed only slight hyperplasia of the mucosal epithelium confined to the limiting ridge in approximately 30% of the cases. All non-diabetic female rats showed neither proliferative changes nor the inflammatory process in the mucosa. Immunohistochemically, COX-2 and iNOS were positive in these chronic suppurative inflammatory lesions accompanied by proliferative squamous epithelium. From these results, it is suggested that chronic inflammatory processes play an important role in the pathogenesis of alloxan-induced SCC. (1) The diabetic conditions are characterized by low-level blood insulin, (2) and glucosuria from approximately 40 weeks of age and development of various diabetic complications such as peripheral neuropathy, (3,4) nephropathy (5) and retinopathy (6) in advanced age. Furthermore, these rats had been reported to be an animal model with successful induction of gastric cancer in the lesser curvature of stomach, a common occurrence site of human gastric carcinoma, by the treatment of carcinogens. (7) However, no spontaneous proliferative lesions were described in the alimentary tracts even in the older rats of this strain.In the serial studies for the analyses of pathogenesis of diabetic complications, male and female WBN/Kob rats were given a single dose of alloxan in order to accelerate the diabetic condition. A rat autopsy 50 weeks after treatment with alloxan presented a case of SCC in the forestomach.Alloxan is one of the chemicals that induce loss of insulinproducing islet β-cells and cause a hypoinsulinemic condition and resultant diabetes mellitus in animals. This effect is thought to be mediated by a sequence of redox reactions involving the production of superoxide anion radicals in or near the β-cells. As a neoplastic lesion caused by alloxan injection, β-cell tumors leading to primary injury to the pancreatic islet have been reported in a few rats, (11) but there were no reports of alloxaninduced tumors in organs other than the pancreas. Alloxan is not mutagenic, jud...

ABSTRACT. The prognosis for canine cutaneous mast cell tumor (CCMT) is thought to be correlated with histopathological grading. However, the wide variety of histopathologic types of grade II is one of the most troublesome and difficult points for prognosis. The objective of this study is to determine the prognostic value of surgical margin, ki-67 and cyclin D1 protein expression in grade II tumor. Surgically resected specimens of solitary grade II CCMT from 48 dogs with follow-up periods over 360 days (median was 1080 days) were used in this study. The expression of cyclin D1 and ki-67 proteins was determined by morphometrically using slides stained immunocytochemically, and the correlations among the results, survival rate, and recurrence and/or metastasis rate of each dog were analyzed statistically. The recurrence and/or metastasis and mortality rate in the incomplete surgical excision group within 30 months postoperatively were higher than that of the complete surgical excision group. In the incomplete surgical excision group, dogs with low positive staining of ki-67 had a significantly better survival, but the recurrence and metastasis rate and ki-67 positivity failed to show a significant correlation. Only a small number of cases showed cyclin D1-positive tumor cells, but most of them had a poor outcome with a high recurrence rate. In grade II CCMT, incomplete excision induced a relatively high metastasis rate and poor prognosis. Ki-67 positivity is a marker for the estimation of overall survival in incomplete surgical excision cases. Cyclin D1 positivity was low and may not have a prognostic role. KEY WORDS: canine, cyclin D1, ki-67, mast cell tumor, skin.J. Vet. Med. Sci. 69(11): 1117-1121, 2007 Cutaneous mast cell tumors (CCMT) are the most common round cell neoplasm in dogs, accounting for 7 to 21% of all skin tumors [12,16] The most accurate and commonly used prognostic factor is histological grade. Among the histological grading systems, Patnaik's method has been the most commonly used around the world [3,17], and the prognostic significance of this method was confirmed in other studies [1,7,8,23]. According to Patnaik's system, CCMT is classified into 3 categories on the basis of morphologic grading: grade I tumors are the most differentiated and have a good prognosis, grade III tumors are poorly differentiated with a poor prognosis, and grade II shows an intermediate differentiation with good to poor prognosis. Using this grading system, the prognosis of grade I and III tumors can be readily determined well [17]. However, other parameters have been needed for precise prognosis of grade II tumors, which have shown an inconsistent prognosis, the marked degree of inter-observer variation and accounted for 40% or 59% of CCMT [15,17].The relationships among surgical margin and prognosis or recurrence have been reported by several researchers. In grade II tumors, a complete surgical margin accurately predicted a good prognosis [21,27]. The frequency of recurrence in the complete surgical excision cases w...

Abstract. Among the intestinal tumors of hematopoietic cell origin, lymphoma is the most common in the dog. Herein, we characterized the clinical and pathologic features of 11 dogs (average age, 10.6 6 2.5 years) with T-cell lymphoma of the intestinal tract with eosinophil infiltrates. No sex predominance was apparent. All had localized tumor masses in the small intestine. Grossly, the intestinal wall was thickened, and the lumen of the affected intestine was usually narrowed. Microscopically, we observed transmural diffuse invasion of round to pleomorphic tumor cells. Tumor cells showed varying morphology, from scanty to abundant cytoplasm, and round to ovoid nuclei with scattered to dense chromatin. In seven of the dogs, tumor cells had infiltrated into the epithelium. All showed infiltration of eosinophils and all 11 tumors had a T-cell phenotype (CD3+, CD792). Only one tumor stained positive for the mast cell marker c-kit and none was positive for mast cell tryptase. We did not observe ultrastructurally apparent granules in any of the tumor cells. These results suggest that, in dogs, T-cell lymphomas of intestinal origin resemble mast cell tumors of intestinal origin with respect to cell structure and eosinophil infiltration. Therefore, in the absence of epitheliotropism, it is difficult to confirm the differential diagnosis without immunostaining for mast cell and lymphocyte markers, including mast cell tryptase, c-kit, CD3, and CD79.

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