Proposal of a 2-tier histologic grading system for canine cutaneous mast cell tumors to more accurately predict biological behavior.

Currently, prognostic and therapeutic determinations for canine cutaneous mast cell tumors (MCTs) are primarily based on histologic grade. However, the use of different grading systems by veterinary pathologists and institutional modifications make the prognostic value of histologic grading highly questionable. To evaluate the consistency of microscopic grading among veterinary pathologists and the prognostic significance of the Patnaik grading system, 95 cutaneous MCTs from 95 dogs were graded in a blinded study by 28 veterinary pathologists from 16 institutions. Concordance among veterinary pathologists was 75% for the diagnosis of grade 3 MCTs and less than 64% for the diagnosis of grade 1 and 2 MCTs. To improve concordance among pathologists and to provide better prognostic significance, a 2-tier histologic grading system was devised. The diagnosis of high-grade MCTs is based on the presence of any one of the following criteria: at least 7 mitotic figures in 10 high-power fields (hpf); at least 3 multinucleated (3 or more nuclei) cells in 10 hpf; at least 3 bizarre nuclei in 10 hpf; karyomegaly (ie, nuclear diameters of at least 10% of neoplastic cells vary by at least two-fold). Fields with the highest mitotic activity or with the highest degree of anisokaryosis were selected to assess the different parameters. According to the novel grading system, high-grade MCTs were significantly associated with shorter time to metastasis or new tumor development, and with shorter survival time. The median survival time was less than 4 months for high-grade MCTs but more than 2 years for low-grade MCTs.

Variation among pathologists in the histologic grading of canine cutaneous mast cell tumors with uniform use of a single grading reference.

Ten veterinary pathologists independently assigned histologic grades to the same 60 canine cutaneous mast cell tumors using the Patnaik classifications. The degree of agreement in grading among the pathologists was compared with the degree of agreement among the same pathologists in a previous study, in which each pathologist used the reference for grading that he/she uses routinely. Mean agreement improved significantly from 50.3% to 62.1% with uniform use of the Patnaik classifications (P = 0.00001), suggesting that there is value in uniform application of a single grading scheme for canine cutaneous mast cell tumors. Agreement among pathologists was still not 100%, suggesting that a more objective grading scheme should be developed and that other histologic indicators of prognosis should be investigated.

Body weight suppression in broilers naturally infected with avian leukosis virus subgroup J.

Broiler progeny were hatched from avian leukosis virus (ALV)-negative and ALV subgroup J (ALV-J)-positive breeders. ALV-J infection in progeny was identified by p27 antigen capture enzyme-linked immunosorbent assay and reverse transcriptase-polymerase chain reaction specific for ALV-J performed on serum or plasma samples obtained at hatch. Hatch weights did not differ between ALV-negative broilers and ALV-J-positive broilers. Body weights of ALV-J-positive broilers were 64.4% of those of ALV-negative broilers at 1 wk of age. At 8 wk of age, weights of broilers with congenital ALV-J infection were still only 63.8% of those of ALV-negative broilers. No other concurrent pathogen was detected in either group of broilers. These findings indicate that congenital ALV-J infection is associated with significant weight suppression in broilers in the absence of other pathogens.

Intravascular cartilaginous emboli in the spinal cord of turkeys.

A flock of 15-wk-old tom turkeys experienced an acute onset of paresis and ataxia in 75% of the birds after handling. Cartilaginous emboli were found in the spinal cord vasculature from one of five turkeys at this initial presentation. Most of the flock recovered within 6 days, but 3% remained paretic. Myelomalacia was present in three turkeys that failed to recover. Two of these turkeys had cartilaginous and osseous emboli within the medullary spaces of the vertebral bodies, internal vertebral venous sinuses, and spinal cord. The third turkey had vascular and spinal cord necrosis consistent with thrombosis and resultant ischemia. These changes suggest that turkeys may be susceptible to a syndrome analogous to fibrocartilaginous embolism of the spinal cord in mammals. The articular cartilage of the vertebral body endplate may be the source of the emboli. The turkeys with emboli had articular cartilage defects consisting of matrix eosinophilia, chondrocyte loss, multicellular cluster formation, cartilage detachment, and cartilage clefts. Cartilaginous emboli in the spinal cord should be considered as a potential cause for acute paresis and ataxia, especially in flocks with preexisting abnormalities of the vertebral articular cartilage surfaces.

Renal osteosarcoma in a dog.

A seven-and-a-half-year-old dog presented with anorexia, lethargy and haematurla. A 1.8 kg abdominal mass was excised and determined to be a primary renal osteosarcoma. Haematuria was observed five months after surgery and the tumour was radiographically determined to have recurred locally. The dog was euthanased 12 days later due to refractory pain and anorexia. Although osteosarcomas are expected to develop distant metastases, this dog was euthanased due to clinical evidence of local tumour recurrence. Haematuria was an indication both of initial tumour development and later recurrence.

Hepatocellular proliferation and hepatocarcinogen bioactivation in mice with diet-induced fatty liver and obesity.

Human liver cancer is in part associated with obesity and related metabolic diseases. The present study was undertaken in a mouse model of diet-induced obesity (DIO) and hepatic steatosis, conditions which can be associated with hepatic neoplasia, to determine whether the rates of cell proliferation or hepatocarcinogen bioactivation were altered in ways which could facilitate hepatocarcinogenesis. DIO mice were generated by feeding C57BL/6 (B6) male mice a high-fat diet beginning at 4 weeks of age; age-matched conventional lean (LEAN) B6 mice fed a low fat diet (10% Kcal from fat) were used for comparison. Groups of 28 week old DIO and LEAN mice were dosed with the bioactivation-dependent DNA-reactive hepatocarcinogen 2-acetylaminofluorene (AAF), at 2.24 or 22.4 mg/kg, given by gavage 3 times per week for 31 days, or received no treatment (DIO and LEAN control groups). Compared with the LEAN control group, the DIO control group had a higher mean body weight (16.5 g), higher mean absolute (1.4 g) and mean relative (25.5%) liver weights, higher (394%) liver triglyceride concentrations, and an increased incidence and severity of hepatocellular steatosis at the end of the dosing phase. The DIO control group also had a higher mean hepatocellular replicating fraction (31% increase, determined by proliferating cell nuclear antigen immunohistochemistry). Hepatocarcinogen bioactivation, based on formation of AAF DNA adducts as measured by nucleotide (32)P-postlabeling, was similar in both DIO and LEAN AAF-dosed groups. Thus, hepatocellular proliferation, but not hepatocarcinogen bioactivation, was identified as an alteration in livers of DIO mice which could contribute to their susceptibility to hepatocarcinogenesis.

Cardiomyopathy in broiler chickens congenitally infected with avian leukosis virus subgroup J.

Dilated cardiomyopathy and ascites in broiler chickens are frequently associated with rapid growth and pulmonary hypertension, but can be associated with some avian leukosis virus (ALV) infections. The novel subgroup J of ALV has a high cardiac tropism, but dilated cardiomyopathy has not been reported previously. We report a dilated cardiomyopathy incidence of 11.1% in broiler chickens congenitally infected with ALV subgroup J (ALV-J). Gross lesions included severe body weight suppression, cardiomegaly with biventricular dilation, right ventricular hypertrophy, visceral congestion, and ascites. Cardiac myocytes and Purkinje fibers contained 2- to 10-microm intracytoplasmic magenta inclusions that contained ALV-J-specific nucleic acid. Ultrastructurally, inclusions contained ribosomes and immature virions and were associated with myofibril disruption and disarray. Peracute centrilobular hepatic necrosis was present in most cases. ALV-J-associated cardiomyopathy may involve a direct viral effect on cardiac myocytes and Purkinje fibers.

Uterine leiomyomas in two Vietnamese pot-bellied pigs (Sus scrofa).

Two Vietnamese pot-bellied pigs (Sus scrofa) were euthanatized after they developed abdominal distension. Necropsy of both pigs revealed large myometrial neoplasms and cystic endometrial hyperplasia. Multiple discrete smaller myometrial neoplasms were also observed in one pig; however, distant metastases were not observed in either animal. The tumors were diagnosed as leiomyomas on the basis of histologic examination and immunohistochemistry. This is the first detailed report of uterine leiomyomas in swine, and it is suggested that this diagnosis may become more common as more aging pigs are examined.

Localization of avian leukosis virus subgroup J in naturally infected chickens by RNA in situ hybridization.

The novel subgroup J of avian leukosis virus (ALV-J) has emerged as a significant cause of myeloid neoplasia and weight suppression in broiler chickens. We investigated viral tropism using RNA in situ hybridization (ISH) in naturally infected chickens. Formalin-fixed tissues were collected from 12-day-old embryos (seven infected, two control) and from 0-week-old (four infected, one control), 3-week-old (five infected, one control), 6-week-old (five infected, one control), and 9-week-old (10 infected, two control) chickens naturally infected with ALV-J in ovo. A 636-base antisense riboprobe complementary to the 3' and 5' ends of the pol and env viral genes, respectively, was constructed. Strong positive staining was present in cardiac myocytes, Purkinje fibers, vascular and pulmonary smooth muscle, renal glomeruli, distal tubules, and pituitary glands. Light staining was present in gastrointestinal smooth muscle, thyroid and adrenal glands, and follicular medullae in the cloacal bursa. Staining was not present in any hematopoietic precursors. Tissues from newly hatched chicks exhibited the strongest and most consistent staining, whereas staining in embryos was minimal. RNA ISH confirmed the presence of ALV-J-specific nucleic acid within cytoplasmic inclusions in cardiac myocytes, Purkinje fibers, pituitary glands, and renal glomeruli. Viral tropism for cardiac myocytes and Purkinje fibers may relate pathogenetically to the cardiomyopathy and congestive heart failure described in index chicken flocks infected with ALV-J. Viral tropism for endocrine organs may relate pathogenetically to the weight suppression associated with infection.

Histology and immunohistochemistry of seven ferret vaccination-site fibrosarcomas.

The anatomical location, histology, and immunohistochemistry of 10 ferret dermal and subcutaneous fibrosarcomas were examined. Seven of the 10 tumors were from locations used for vaccination. All fibrosarcomas contained spindle-shaped cells surrounded by variable quantities of connective tissue stroma. However, vaccination-site fibrosarcomas (VSFs) subjectively contained a higher degree of cellular pleomorphism. Multinucleated cells were present in three of seven VSFs but not in any of the nonvaccination-site fibrosarcomas (NVSFs). Large histiocytic cells, interpreted as macrophages, containing intracytoplasmic basophilic granular material were observed in two VSFs but not in any of the NVSFs. Five VSFs contained peripheral lymphoplasmacytic aggregates. Immunohistochemically, three VSFs stained with anti-smooth muscle actin antibodies and one stained with antibodies against desmin. No expression of muscle cytoskeletal filaments was observed in any NVSF. Filaments interpreted as actin were visible in both the VSFs examined ultrastructurally. One of the VSFs examined ultrastructurally contained intracytoplasmic crystalline material. The preferential development of subcutaneous fibrosarcomas in vaccination sites suggests that, as in cats, vaccination may promote local sarcoma development in ferrets. Additionally, some of the histologic, immunohistochemical, and ultrastructural features of these tumors are similar to those reported for feline vaccine-associated sarcomas. To the authors' knowledge, vaccination has not previously been reported to be oncogenic in any species other than cats.

Heterophil function and resistance to staphylococcal challenge in broiler chickens naturally infected with avian leukosis virus subgroup J.

Avian leukosis virus subgroup J has a high tropism for myeloid lineage cells and frequently induces neoplastic transformation of myelocytes. The impact of congenital avian leukosis virus subgroup J infection on the function of circulating heterophils and susceptibility to staphylococcal infection was investigated. Six-week-old broiler chickens negative for exogenous avian leukosis viruses or congenitally infected with avian leukosis virus subgroup J were inoculated intravenously with 10(6) colony-forming units of Staphylococcus aureus, and pre- and postinoculation heterophil function was assessed. All chickens developed a leukocytosis with heterophilia after inoculation, but total leukocyte and heterophil counts were significantly higher in leukosis-negative chickens than in virus-infected chickens. Tenosynovitis was more severe in leukosis-negative chickens, and 2/10 (20%) of the virus-infected chickens had no histologic evidence of tenosynovitis. Osteomyelitis in the tibiotarsus or tarsometatarsus developed in 5/10 (50%) of the chickens in each group. S. aureus was recovered from the hock joint of 6/10 (60%) of the chickens in each group. Heterophils from all chickens exhibited similar phagocytic ability pre- and postinoculation. Heterophils from virus-infected chickens exhibited less bactericidal ability preinoculation than did heterophils from leukosis-negative chickens. However, postinoculation bactericidal ability was similar in both groups. Avian leukosis virus subgroup J provirus was present in heterophils isolated from congenitally infected chickens. Heterophils isolated from broiler chickens congenitally infected with avian leukosis virus subgroup J exhibit no significant functional deficits, and infected and uninfected chickens exhibit similar susceptibility to staphylococcal infection.

Gastric amebiasis due to Entamoeba histolytica in a Dama wallaby (Macropus eugenii).

A 1.5-year-old captive female Dama wallaby (Macropus eugenii) died after a 3-month period of progressive weight loss, anorexia, bloat, and diarrhea. Histopathologic examination revealed numerous Entamoeba histolytica trophozoites within the gastric mucosa and, less frequently, gastric submucosa and submucosal vessels. Immunofluorescent antibody testing confirmed the identity of the trophozoites as E. histolytica. The trophozoites were associated with mild glandular epithelial necrosis, mucosal erosions, and lymphoplasmacytic inflammation. E. histolytica most commonly causes necrotizing and ulcerative colitis in humans and captive nonhuman primates, and it causes necrotizing and ulcerative gastritis in nonhuman primates with sacculated stomachs adapted for leaf fermentation. Rare cases of gastric amebiasis also have been been reported in captive macropods, which also have complex sacculated stomachs. To our knowledge, this is the first report confirming E. histolytica as the cause of gastric amebiasis in a wallaby. The zoonotic potential of this infection in macropods is uncertain.