Late Humoral Rejection in a Cardiac Transplant Recipient Treated With the Anti-CD20 Monoclonal Antibody Rituximab

Humoral or vascular rejection results from a B cell-mediated production of immunoglobulin (Ig) G antibody against a transplanted organ, producing immune complex deposition on the vascular endothelium, activation of the complement cascade, generation of endothelial dysfunction, and regional ischemic injury. Antibody-mediated rejection, which may be accompanied by hemodynamic compromise, is associated with reduced long-term graft survival. Patients believed to be at an increased risk of developing humoral rejection include women, particularly those with high levels of panel reactive antibodies, cytomegalovirus seropositivity, and positive cross matches, and subjects with prior sensitization to OKT3. Treatment options for humoral rejection include plasmapheresis to lower the circulating immunoglobulin levels followed by high-dose cyclophosphamide to reduce the B-cell population. Other modalities include total lymphoid irradiation, photophoresis, splenectomy, and, for treatment failures, retransplantation. Rituximab is a chimeric humanized monoclonal antibody directed against the pan B-cell surface molecule, CD20. It is approved for the treatment of low-grade B-cell non-Hodgkin's lymphoma. It has also been used successfully for the treatment of posttransplant B-cell lymphoproliferative disease. We report a case of late humoral rejection successfully treated with rituximab.

Comparability of national death index plus and standard procedures for determining causes of death in epidemiologic studies

PURPOSE

To determine whether causes of death obtained through National Death Index (NDI) Plus are comparable to those obtained by requesting death certificates from state vital statistics offices and having deaths coded by contractor nosologists.

METHODS

The authors compared underlying cause of death codes obtained from NDI Plus with those assigned by contractor nosologists for a sample of 250 known decedents.

RESULTS

The underlying cause of death codes differed for 18 (7%) of 249 successful matches. Independent coding by an expert National Center for Health Statistics (NCHS) nosologist trainer revealed that seven of these had an NDI Plus code that matched the code provided by the NCHS nosologist and a contractor nosologist code that did not match the NCHS nosologist code, seven had a contractor nosologist code that matched the NCHS nosologist code and an NDI Plus code that did not match the NCHS nosologist code, and four had both an NDI Plus and a contractor nosologist code that did not match the NCHS nosologist code. The level of disagreement with the NCHS nosologist and the organ systems involved were similar for NDI Plus and the contractor nosologist.

CONCLUSIONS

The authors report that NDI Plus provides comparable information within a substantially shorter time period for most states and, for known decedents, at about half the cost of standard procedures.

On the association between canine malignant lymphoma and opportunity for exposure to 2,4-dichlorophenoxyacetic acid

In response to criticisms raised regarding a case-control study of canine malignant lymphoma, the results of several ancillary analyses are reported. The case-control study demonstrated a significant association between risk for canine malignant lymphoma and the opportunity for exposure to 2,4-dichlorophenoxyacetic acid herbicides. It is demonstrated that risk estimates do not vary by type of control group (i.e., tumor control or nontumor control group), by method of response (i.e., self-administered or telephone interview), or by geographic area. Questions related to the potential for referral bias, supposed inconsistencies in subject responses regarding frequency of herbicide use, and ambiguities regarding exposure classification are also examined.

A cohort study of the effects of Vietnam service on testicular pathology of U.S. military working dogs

Using histopathologic diagnoses made on necropsy material from 3,024 military working dogs (MWDs) who died from 1968 to 1973, we analyzed the effect of military service in the Republic of Vietnam on testicular pathology. Among 1,048 MWDs that died in Vietnam and had no reported developmental risk factors for testicular disease, significant excesses of testicular hemorrhage, epididymitis/orchitis, sperm granuloma, testicular degeneration, and seminoma were evident. Among 126 MWDs with prior Vietnam service who died at other duty stations outside Vietnam from 1968 to 1973, significant excesses of testicular degeneration and seminoma were likewise evident. Among 136 MWDs with prior Vietnam service that later died from 1974 to 1980, seminoma continued to be diagnosed in significant excess. In each instance, the odds ratio for the association between Vietnam service and seminoma was 2.0 or greater. Analysis of ever service by Corps Tactical Zones showed significant excesses of seminoma with each Corps area of service compared to Vietnam-era MWDs, but risk was highest in I Corps, particularly at Da Nang Port and Da Nang Air Base. This finding with respect to I Corps is consistent with certain human studies in Vietnam veterans and points to the need for further investigation of possible environmental exposures, particularly those associated to a greater extent with service in I Corps.

U.S. military working dogs with Vietnam service: definition and characteristics of the cohort

We verified and corrected inaccuracies in descriptive profile information on military working dogs (MWDs) that died from 1965 to 1980 and were reported in the Armed Forces Institute of Pathology Registry of Veterinary Pathology. Using other available military records, we determined which dogs served in Vietnam. Identified were 3,895 MWDs with a unique identity tattoo that served in Vietnam, of which 2,389 served exclusively with U.S. military forces and died in Vietnam. Another 479 Vietnam veteran MWDs completed their service elsewhere. This overall effort resulted in signalment corrections, generally age at death, in 21% of the Registry MWD accessions during the study period. The improved definition and characterization of the Vietnam cohort will lead to greater precision in epidemiologic investigations of the health effects from the Vietnam experience in U.S. military working dogs.

Case-control study of canine malignant lymphoma: positive association with dog owner's use of 2,4-dichlorophenoxyacetic acid herbicides

A hospital-based case-control study of companion dogs examined the risk of developing canine malignant lymphoma associated with the use of chemicals in and about the home. Information from a self-administered owner questionnaire and/or a telephone interview of about 491 cases, 466 nontumor controls, and 479 tumor controls indicated that owners in households with dogs that developed malignant lymphoma applied 2,4-dichlorophenoxyacetic acid (2,4-D) herbicides to their lawn and/or employed commercial lawn care companies to treat their yard significantly more frequently than control owners (odds ratio = 1.3). In addition, the risk of canine malignant lymphoma rose to a twofold excess with four or more yearly owner applications of 2,4-D. The findings in this study are consistent with occupational studies in humans, which have reported modest associations between agricultural exposure to 2,4-D and increased risk of non-Hodgkin's lymphoma, the histology and epidemiology of which are similar to those of canine malignant lymphoma. The present study suggests that human health implications of 2,4-D exposure in the home environment should receive further investigation.

Excess of seminomas observed in Vietnam service U.S. military working dogs

During the Vietnam War, US military working dogs served with their companion dog handlers in close proximity, sharing common exposures to war-related activity, many zoonotic infectious agents, chemical pesticides, phenoxy herbicides, and extensive use of therapeutic drugs. To gain insight into the effects of the Vietnam experience, we investigated the occurrence of neoplasms in military working dogs based on standard necropsy examination by the Armed Forces Institute of Pathology. We observed that these dogs experienced significant elevated risks for testicular seminoma and, independently, testicular dysfunction. Experimental evidence shows testicular dysfunction and impaired spermatogenesis in laboratory animals exposed to phenoxy herbicides, dioxin, or tetracycline, and antibiotic used extensively in military working dogs in Vietnam. Because an unexplained significant decrease in sperm quality in Vietnam veterans has been observed by the Centers for Disease Control, further research is warranted if we are to clarify military service in Vietnam as a risk factor for testicular dysfunction. The testis should be made a priority site in the study of Vietnam experience-related cancers.

Effects of ear type and weather on the hospital prevalence of canine otitis externa

A retrospective study of 8975 dogs seen at 15 university veterinary medical teaching hospitals in North America (1975 to 1978) found that dogs with pendulous ears and heavy ear canal hair had significantly (P less than 0.01) more otitis externa than dogs with other ear types. Dogs with erect ears, regardless of the amount of ear canal hair, had less risk (P less than 0.01) of the disease than mongrel dogs. Direct evidence is available for the first time showing that monthly variations in ambient temperature, rainfall and relative humidity explain, to a large extent, the monthly variations in the hospital prevalence of canine otitis externa in different geographic regions.

Epidemiological features of 5009 cases of equine cryptorchism

Data from 16 North American veterinary university teaching facilities, 5009 cryptorchid horses, were analysed using relative risk methodology. In five breeds (Thoroughbred, Standardbred, Morgan, Tennessee Walking horse and Arabian), cryptorchism was diagnosed significantly (P less than 0.05) less frequently than expected by their representation in the hospital population. Three breeds, (Percheron, American Saddle horse and American Quarterhorse), plus ponies (as a group) and crossbred horses were significantly over-represented within the series. The over-representation of Quarter-horses was evident at each veterinary teaching facility. Other developmental defects and testicular tumours diagnosed in cryptorchid horses were presented. Analysis of the frequency of diagnosis of second anomalies among cryptorchids showed testicular hypoplasia to occur significantly more often, and inguinal and umbilical hernias less often, than expected (P less than 0.05).

Hospital incidence of hypospadias in dogs in North America

A review of medical records from 17 North American university veterinary medical teaching hospitals identified 66 dogs with hypospadias. Males predominated (15:1) and cryptorchidism was the most commonly diagnosed second anomaly, often associated with intersexuality. Fifteen cases, diagnosed at 10 different university hospitals, were Boston terriers, strongly suggesting that this breed has a familial predisposition for hypospadias. Male mongrels, as a group, were seen in approximately the same proportion as their representation in the hospital population, suggesting other components in the aetiology of the condition. If maternal histories are obtained as new cases are identified, a better understanding of the factors associated with the aetiology of the condition may be possible.

Canine cryptorchism and subsequent testicular neoplasia: case-control study with epidemiologic update

A retrospective study of 2,912 cryptorchid dogs identified 14 breeds with significantly high risk. Among six distinct closely interrelated breed groups (e.g., toy, miniature, and standard poodles), the risk in the smaller breed was always greater than that in the larger relative, suggesting that genetically influenced maldescent could be, in part, related to physical size or the rate of growth of the involved structures. Testicular tumors were diagnosed in 5.7% of the cryptorchid dogs; half had only Sertoli cell tumors, one-third had only seminomas. The relative risk for Sertoli cell tumor or seminoma was not directly related to a familial risk for cryptorchism. Using the health experience of a control population composed of male dogs with anal sac disease (N = 4,184), there is an estimated relative risk of 9.2 in cryptorchid dogs to develop a testis tumor (95% confidence interval, 5.9-14.3) and 4.2 in dogs with inguinal hernia (95% confidence interval, 1.8-9.5). Considering that the anatomical development of the genital tract, testis descent, and tunic relationships in dog are very similar to that in man, and that the associations of cryptorchism and inguinal hernia with testis neoplasms are also similar, the dog should be an excellent model system to further investigate the causes of human cryptorchism.

Juvenile renal disease in Doberman Pinscher dogs

Renal failure was diagnosed in 22 young Doberman Pinscher dogs. The clinical findings were anorexia, weight loss, vomiting, lethargy, polydipsia, polyuria, and dehydration. Laboratory findings were azotemia, hyperphosphatemia, lymphopenia, nonregenerative anemia, hypercholesterolemia, and proteinuria. The kidneys were characterized pathologically by glomerular sclerosis, cystic glomerular atrophy, tubular dilatation, tubular atrophy, mononuclear interstitial inflammation, interstitial fibrosis, interstitial mineralization, and hyperplasia of the collecting duct epithelium.

Canine biliary carcinoma: epidemiological comparisons with man

A retrospective study of abstracted data representing 1.1 million hospital examinations of dogs at veterinary university teaching facilities identified 77 with bile duct carcinoma. Using the hospital population, based on patient years at risk, as the expected frequency of particular zoographic characteristics, there was a suggestion of a familial (breed) predisposition in Labrador retrievers and limited evidence of a sex differential. Because mongrel dogs displayed about the same frequency of bile duct cancer as all breeds combined, other causal factors, besides genetics, are implied. A possible association was detected between canine cholangiocarcinoma and host infection by canine hookworms and/or whipworms. Human infection from hookworms (Necator americanus) and whipworms (Trichuris trichiura) is common in the southern rural areas of the U.S.A. (e.g. Appalachia), and tropical and sub-tropical countries of Africa, Central and South America, where there have been unexplained high rates reported for human biliary cancer. It is possible that the presence of these blood-letting nematodes, like a number of other parasites (ascarids, flukes and protozoa), may be related to the occurrence of human cholangiocarcinoma.

Mortality patterns among US veterinarians, 1947-1977: an expanded study

Causes of death among 5016 white male veterinarians identified from obituary listings in the Journal of the American Veterinary Medical Association were compared to a distribution based on the general US population. Proportions of deaths were significantly elevated for cancers of the lymphatic and haematopoietic system, colon, brain, and skin. Fewer deaths were observed than expected for cancers of the stomach and lung. Although socio-economic and methodological factors may be involved, the patterns suggest that sunlight exposure is responsible for the excess of skin cancer among veterinarians whose practices are not exclusively limited to small animals, and ionizing radiation exposure contributes to the excess of leukaemia among veterinarians practising during years when diagnostic radiology became widely used. Mortality was also high for motor vehicle accidents and suicides, but low for diseases of the respiratory system.

Carcinoma of the nasal cavity and paranasal sinuses in dogs: descriptive epidemiology

A retrospective study of medical records from 15 veterinary university teaching hospitals and clinics yielded 504 dogs with microscopically confirmed primary carcinoma of the nasal cavity or paranasal sinuses. When compared to the hospital population at risk, males showed a 1.3 fold excess risk (p less than or equal to 0.05), adjusted for age and gonadal status, compared to females. The male excess persisted from 1 through 14 years of age. Dolichocephalic dogs (specifically the Collie and Sheltie) had a higher risk than other dogs and brachycephalic dogs had a lower risk, but these variations may not be a simple function of skull type. Seven breeds of dogs were identified with a significantly high risk and two with low risk. Among breeds with mesaticephalic type skulls, risk was not associated with adult body weight, used as a measure of body size and tidal air requirement. Mongrel dogs, often spared from other types of cancer, displayed the same risk as all breeds combined, suggesting the influence of environmental factors.

Bladder cancer in pet dogs: a sentinel for environmental cancer?

Proportional morbidity ratios (PMRs) were calculated for cancers, by site or type, in 8760 pet dogs seen at 13 veterinary medical teaching hospitals in the United States and Canada. A significant positive correlation was seen between the PMRs for canine bladder cancer and the overall level of industrial activity in the host county of the hospital. An analysis of mortality from bladder cancer among white men and women in the same US counties showed similar correlations with industrial activity. Canine bladder cancer could be a sentinel condition whose investigation in locales might lead to early identification of carcinogenic hazards in the general environment.

Epidemiological features of feline mammary carcinoma

An epidemiological survey involving 132 cats with mammary neoplasia, seen at 15 North American veterinary medical teaching hospitals, was conducted. The ratio of malignant to benign tumours was 9:1. There were 113 cases of carcinomas of all types (including two males), with adenocarcinoma being the predominant cell-type. Relative risk analysis indicated that the Siamese breed had twice the risk (P less than 0.01) of developing mammary carcinoma compared to all breeds combined. The age at diagnosis in Siamese females tended to be younger than in other breeds. Comparison of clinical and pathological features of breast cancer suggests that the cat is an appropriate surrogate for the experimental study of human breast cancer. The apparent lack of oestrogen dependency in feline breast cancer also suggests that the cat may be especially suited for evaluating therapeutic regimens for breast cancers that do not respond to hormonal manipulation.

Epidemiologic features of canine hypothyroidism

This study investigates the epidemiologic features of 3,206 dogs diagnosed with hypothyroidism (including myxedema) from 1.1 million dogs seen at 15 veterinary teaching hospitals between March, 1964 and June, 1978. Nine breeds found to be at high-risk for hypothyroidism were: golden retrievers, Doberman pinschers, dachshunds, Shetland sheepdogs, Irish setters, Pomeranians, miniature schnauzers, cocker spaniels, and Airedales. Two breed with a significant deficit of risk were German shepherds and mixed breed (mongrel) dogs. Age risk was greatest among younger dogs of high-risk breeds, further suggesting a genetic component to the etiology of this disease. In contrast, low-risk dogs had increasing relative risk through nine years of age. Spayed female dogs displayed a significantly higher risk when compared to intact females. Though not statistically significant, male castrated dogs had 30% more hypothyroidism compared to their intact counterparts. Among the case series were 91 endocrine and hormone-related neoplasms and 198 other endocrine-related disorders. Further studies linking canine hypothyroidism to other conditions, particularly cancer, could provide valuable insight into human disease experience.

Cancer and other causes of death among U.S. veterinarians, 1966-1977

Causes of death among 1,551 white male veterinarians identified from obituary listings in the Journal of the American Veterinary Medical Association were compared to an expected distribution based on the general US population. The proportion of deaths was significantly high for particular neoplasms, especially leukemia and Hodgkin's disease, and cancers of the brain and skin. Although socioeconomic and methodologic factors may be involved, the excesses were primarily among veterinarians in clinical practice, raising the possibility that specific occupational exposures may be carcinogenic. Mortality was also relatively high for motor vehicle accidents, suicides and asthma, but low for lung cancer and other diseases of the respiratory system.

Risk factors associated with canine heartworm infection

Risk factors associated with canine heartworm infection were determined by screening medical records from the Veterinary Medical Data Program of June 1964--May 1976. Data represented were from 14 colleges and schools of veterinary medicine in the United States and Canada. A total of 3,655 dogs were infected. Intact male dogs 4 to 7 years old and of the larger hound breeds had the highest relative risk, whereas dogs of smaller breeds, those less than 2 years old, spayed females, and castrated males were at least risk.

Castration for treatment of perianal gland neoplasms in the dog

Neoplasms of the perianal gland are common in the dog, particularly the male. Adenomas of the gland develop about 4.5 times more often than do carcinomas of the gland. The adenoma is hormone dependent; thus, castration without excision of the tumor has been successful in promoting regression without recurrence. Microscopic examination of the testes from dogs with perianal gland neoplasms has revealed 1 in 10 with tubular atrophy and 1 in 3 with testicular neoplasia. Interstitial cell tumors have been seen more often than other cell types of testis tumors.

Epizootiologic features of canine hydrocephalus

In a retrospective study of hydrocephalus (of congenital origin) diagnosed in 564 dogs, 11 breeds (including 8 "toy" breeds) were identified as being a significantly high risk. An inverse relationship between risk and body size was detected. The smaller the dam at maturity, either in height at the shoulder or body weight, the greater the risk of hydrocephalus in the offspring.

Patent ductus arteriosus in the dog: a retrospective study of radiographic, epidemiologic, and clinical findings

Twenty-seven cases of patent ductus arteriosus (PDA) in the dog, which were confirmed by cardiac catheterization, surgical exploration, or at necropsy, were reviewed. A machinery murmur, electrocardiographic evidence of left ventricular enlargement, and radiographic evidence of cardiomegaly with an aortic and a pulmonary artery dilatation were consistent features. Surgical repair was successful in 65% of the dogs. The postoperative radiographic and electrocardiographic changes are described. A concomitant congenital defect was present in 2 dogs. The epidemiologic features of 532 dogs identified as having PDA and submitted to the National Cancer Institute's Veterinary Medical Data Program were reviewed. Miniature and Toy Poodles, Pomeranians, and Shetland Sheepdogs were identified as being at high risk for PDA. An excess of females over males was noticed.

Epidemiological features of canine renal neoplasms

A retrospective study of medical records from 13 veterinary university hospitals and clinics yielded 73 cases of confirmed primary neoplasms of the kidney and renal pelvis. Analysis of the 34 cases of renal carcinoma revealed no evidence of familial (breed) predisposition, but an excess risk was identified in males, especially during middle life. The morphological and epidemiological features of canine renal carcinoma are similar to those of renal carcinoma in humans. The dog may be a suitable model for further research into the causes of this cancer.

Epidemiology and toxicology of arsenic poisoning in domestic animals

Arsenic poisoning is one of the more important causes of heavy metal poisoning in domestic animals. Two species--dogs and cattle--are intoxicated more frequently than other animals; yet sporadic instances of poisoning have been observed in cats, horses, and pigs. Cases observed by veterinary clinicians are either peracute, acute, or chronic intoxications. Frequently the initial and only indication that a severe problem exists with peracute poisoning in a cattle herd is dead animals. Chronic intoxications are also observed in cattle. Acute intoxication is the most common form of arsenic poisoning observed and documented in the dog. Also intoxicated dogs were younger, i.e., 2-6 months of age. Arsenic is a severe alimentary tract irritant in domestic animals, and treatment in most instances consists mainly of symptomatic and supportive treatment. The source of intoxication, when it can be determined, is usually dips, sprays, powders, or vegetation contaminated by pesticides containing arsenic.

Hormone-dependent neoplasms of the canine perianal gland

The epidemiological features of 472 dogs with microscopically confirmed neoplasms of the perianal gland are described. These general characteristics suggest etiological factors similar to those responsible for hormone-related neoplasms occurring in human beings. Perianal gland tumors appear to be androgen dependent. Male dogs show a 5.6-fold-increased risk compared with females; endogenous estrogens offer protection and the use of estrogenic hormones is conventional therapy for the benign lesion. Both sexes of the cocker spaniel breed show excessively high risk, suggesting that this dog family may be a model for genetic studies that could be relevant to familial aggregations of hormone-related tumors in men and women. Adrenocortical hormones may play a role in the development of the tumor in female dogs. Research into alterations of the biochemical pathways of steroidogenesis in affected female dogs may provide clues to similar conditions in humans.

Canine bladder cancer: epidemiologic features

A retrospective study of medical records from 13 veterinary university hospital clinics yielded 114 dogs with microscopically confirmed primary malignancy of the bladder. When matched to controls, there was no increased frequency to suggest an association of urogenital tumors or anomalies with neoplasms of the bladder. The majority of tumors seen in this study were transitional cell carcinomas. Four breeds were identified with excessive risk for bladder cancer and may serve as models for further research into genetic determinants, such as abnormal tryptophan metabolism. The epidemiologic features of canine bladder cancer were compared with the disease in man. An excess among female dogs may be the result of less frequent urination as compared to male dogs. Assuming an etiology from urine-borne carcinogens applies to spontaneously occurring bladder cancer in dogs, then monitoring the frequency of occurrence of canine bladder cancer may provide an early warning of emerging environmental hazards to man.

Canine testicular tumors: epidemiologic features of 410 dogs

Histologically confirmed testicular tumors were diagnosed in 410 dogs from 12 North American veterinary university hospitals and clinics. Three tumor-cell types, Sertoli cell tumor, interstitial cell tumor and seminoma, were about equally represented. Several breeds were identified with high risk for different testicular tumor-cell types. Cytogenetic and immunogenetic studies of these dog families could offer leads applicable to familial testicular cancer in man. The multiplicity of breeds within the series suggests that, as in man, other factors, in addition to hereditary, play a role in etiology. Cryptorchid dogs appear to have a 13.6 times higher risk of testicular tumor than normal dogs. Additionally, male dogs with an inguinal hernia have an increased risk (4.7) of testis tumors. There were no detectable excesses of other urogenital anomalies or urogenital tumors among the series. The Shetland Sheepdog is suggested as an appropriate model for research into the mechanisms responsible for testicular maldescent and tumorigenesis.

Canine thyroid neoplasms: epidemiologic features

A retrospective study of medical records from twelve veterinary university hospitals-clinics yielded 144 dogs with a confirmed diagnosis of a thyroid neoplasm (25 adenomas and 119 carcinomas). Forty-five of these dogs had additional primary neoplasms. As in man, associated tumors suggested the inherited multiple endocrine adenomatosis, type 1, and a possible syndrome of thyroid and chemoreceptor lesions. Although the female preponderance of human thyroid cancer was not seen in dogs, females showed a much sharper increase in risk with advancing age than did males. Three breeds (beagle, boxer, and golden retriever) had a significantly greater risk for thyroid carcinoma than did all dogs combined, whereas miniature and toy poodles had a low risk. The function of thyroiditis in the origin of thyroid cancer, as suggested by reports of thyroid carcinoma in people with Hashimoto's disease, may be clarified by follow-up studies of beagles which are prone to Hashimoto-type thyroiditis.

Cryptorchism and related defects in dogs: epidemiologic comparisons with man

In a study of 1266 dogs with cryptorchism from a large clinic/hospital series 8 breeds were found to be at excess risk of the defect and 3 breeds at significantly low risk. Review of the medical histories revealed that hip dysplasia, patellar dislocation, defects of the penis and prepuce, and umbilical hernia were excessively associated with cryptorchism. Testicular tumors were diagnosed 10.9 times more commonly among cryptorchid dogs. The epidemiologic features of canine cryptorchism were compared with those in man. Cryptorchid dogs could be used as models for etiologic research.

Occurrence of nervous-tissue tumors in cattle, horses, cats and dogs

From 11 North American veterinary university hospitals and clinics, 248 animals were a confirmed diagnosis of nervous-tissue tumor were identified; 7 tumors were found in cattle, 28 in horses, 14 in cats, 199 in dogs, and none in other species. Tumors were divided for analysis into three categories-glial, meningeal, and peripheral nerve. In cattle and horses, all tumors involved peripheral nerves, the risk of which, in horses, reached a plateau at 4-6 years of age and remained constant thereafter. In cats, the tumors were equally distributed among the three tumor categories whereas, in dogs, twice as many glial tumors as meningeal and peripheral nerve tumors were found. The risk for glial tumors in dogs reached a peak at 10-14 years of age, for meningeal at 7-9 years, and for peripheral nerve at 2-3 and 7-9 years. Three canine breeds-English bulldog, boxer, and Boston terrier-had an excessive rish of glial tumors. Except for an excess of skin tumors in dogs with peripheral nerve tumors, there was no unusual occurrence with second primary neoplasms for any species. There was no detectable predisposition by sex for any of the categories of nervous-tissue tumors among any of the four species. The role of genetic abnormalities associated with nervous-tissue tumors and other etiologic factors (e.g., chronic hypoxia) may be clarified by further studies involving canine breeds of "bulldog" ancestry.