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An 8-year-old castrated male mixed-breed cat presented with an abdominal mass of unknown origin, accompanied by eosinophilia. Autopsy revealed mild-to-severe enlargement of lymph nodes throughout the body and multiple nodules in the lungs. Histopathologically, the lymph nodes showed severe fibroplasia and infiltration by a large number of eosinophils and fewer tumor cells, exhibiting large-sized lymphoid cell morphology. Metastatic lesions of tumor cells with eosinophilic infiltration and fibrosis were observed in the lungs, liver, kidneys, stomach, and intestines. Immunohistochemistry revealed that the tumor cells were positive for CD3 and negative for B cell and mast cell markers. Thus, T-cell lymphoma with eosinophilic infiltration and sclerosing fibroplasia was diagnosed.

The association between pancreatic disorder and abdominal fat necrosis in cattle remains unclear. The pancreases of 29 slaughtered cattle with or without fat necrosis were collected to investigate pathological changes. Japanese Black (JB) cattle were classified into the FN group (with abdominal fat necrosis; n=9) and N group (without fat necrosis; n=5). The pancreases were also collected from 15 Holstein Friesian (HF) cows. All JB cattle showed high body condition scores. Regarding the pathological findings, fatty pancreas which involves adipocyte infiltration into the pancreas and fat necrosis (saponification) were observed in 25 and 27 cases, respectively. Immunohistochemical staining with anti-Iba-1 antibody showed large numbers of macrophages surrounding the saponified fat in the pancreas. CD3-positive T cells were significantly more common in the pancreas of both the FN and N groups compared with the HF group (P<0.05). Furthermore, fibrosis in the pancreas exhibited a correlative tendency with the formation of necrotic fat mass in the peritoneal cavity (P<0.1). These results indicate that obesity leads to increased severity of pancreatic disorder, including fatty pancreas and pancreatitis. The pathological lesions in the pancreas may play a key role in abdominal fat necrosis through the inflammatory process.

A 7-year-old female boxer dog died suddenly without any clinical signs. It was suspected that the dog had arrhythmogenic right ventricular cardiomyopathy (ARVC) due to ventricular premature complexes and ventricular tachycardia at 3 years of age. The final diagnosis of ARVC was confirmed by histological characteristics, such as loss of cardiocytes and fibrofatty replacement, occurring in the right and left ventricular walls. In the cardiocytes, non-lipid vacuoles were observed. Cardiac fibrosis and intimal thickening of the small arteries occurred without fatty replacement in the inner muscle layer including the papillary muscles of the left ventricular wall. This paper describes the pathomorphological details of an ARVC case with coincidental cardiac fibrosis in the inner muscle layer of the left ventricular wall.

Senile systemic amyloidosis (SSA) is a rather common disease in elderly people, but it is very rare in animals, including nonhuman primates. Pathological examination of a 26-year-old male savannah monkey (Cercopithecus aethiops) revealed systemic amyloidosis with severe cardiac fibrosis, and tenosynovial degeneration of the elbow and knee joints. The amyloid deposits were observed predominantly in the heart, lung, intestine and tenosynovium, and were positive for transthyretin (TTR) in immunohistochemistry. Immunohistochemical results, together with the distribution of the amyloid deposited lesions and the age of the monkey, were equivalent to those of human SSA. This is the second case of animal SSA with unprecedented TTR amyloid deposited lesions of the tenosynovium resembling human SSA. There may be a genetic factor that makes this species susceptible to SSA, since SSA has been reported in no other mammal besides humans.

The Ito cell (fat-storing cell) lies in perisinusoidal space of liver and has a variety of functions. We investigated the immunohistochemistry and ultrastructure of Ito cells in normal and cholestatic livers of broiler chickens. Immunohistochemistry demonstrated that Ito cells expressed HHF35 muscle actin, vimentin, desmin, glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), chromogranin A and cytokeratins in normal livers. These cells were diffusely scattered throughout the lobules. Livers treated with extrahepatic bile duct ligation (BDL) showed cholestasis, fibrosis, proliferation of biliary ductules and Ito cells. The Ito cells were frequently found in fibrotic areas and were larger in size with more extensive immunoreactivity than those of normal livers. Ultrastructural study demonstrated that Ito cells were closely associated with the production of collagen fibers in BDL livers. These findings suggest that Ito cells actively react against hepatocytic injuries and play a major role in the hepatic fibrogenesis of cholestatic livers of chickens.

Five racehorses in apparently normal condition succumbed to sudden cardiac death (SCD) during or shortly after intensive training exercise. Cardiopathologic examination was performed. In 1 of the 5 horses, the use of an electrocardiogram (ECG) recording taken continuously for 440 sec enabled us to analyze some of the arrhythmias in the terminal event of SCD. The ECG tracing exhibited the R-on-T phenomenon following a pair of ventricular premature contractions (VPCs). The phenomenon rapidly degenerated into ventricular fibrillation, which led to cardiac arrest. In all 5 horses cardiopathologic examination revealed the following lesions: (i) foci of myocardial fibrosis in the right atrium located close to the sinoatrial (SA) node, (ii) fibrotic and/or fibroplastic changes in the upper portion of the interventricular septum, including the atrioventricular (AV) conduction system, and (iii) arterio- and arteriolosclerosis of the SA and AV node vessels. Pathogenetically, the process by which the focal lesions of myocardial ischemia secondary to vascular sclerosis progressed into fibrosis and/or fibroplasia could play a major role in the genesis of arrhythmias. Presumably the fibrotic and/or fibroplastic changes in the area of the AV bundle and its bundle branches are closely related to the onset of fatal ventricular arrhythmias such as VPCs, deteriorating into ventricular fibrillation. SCD in training and racing Thoroughbred horses appears to be due to arrhythmia.

A dwarf male Large White neonate showing various external abnormalities was diagnosed to be chondrodysplasia. Microscopy revealed massive accumulation of eosinophilic homogeneous substance in the renal glomeruli, mainly along the capillary walls. The homogeneous substance, mainly consisted of type-III collagen, was not found in the primitive glomeruli in the superficial cortex, and was most frequently and intensely deposited in the mature glomeruli in the deep cortex. Electron microscopically, the deposits consisted of the collagen fibrils with various structural abnormalities. Glomerular fibrosis might be attributed to in situ production of type-III collagen by glomerular cells with differentiation and maturation, most likely by the mesangial cells.