Canine Gallbladder Infarction: 12 Cases (1993–2003)

A cohort of 12 dogs with severe transmural gallbladder necrosis is described. All dogs had cholecystectomies performed. In six dogs, perforation of the gallbladder was noted at surgery. Eight dogs survived the immediate postoperative period, and four dogs died. Histologically, inflammation was absent or minimal in all cases, suggesting that cholecystitis was not the cause of necrosis. Thrombi ( n = 2) and atheromatous vascular changes ( n = 1) represent possible vascular causes of this condition. The findings of coagulative necrosis in these 12 dogs are compatible with “gallbladder infarction,” and the authors propose this term to describe the histopathologic appearance of the gallbladder.

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.

Activity of an injectable, sustained-release formulation of moxidectin administered prophylactically to mixed-breed dogs to prevent infection with Dirofilaria immitis

OBJECTIVE

To test the ability of a single injection of a sustained-release formulation of moxidectin (moxidectin SR) to protect dogs against heartworm infection for 180 days after inoculation with infective third-stage larvae (L3) of Dirofilaria immitis.

ANIMALS

32 adult mixed-breed dogs.

PROCEDURE

Dogs were allocated to 4 groups on the basis of weight and sex. Dogs were injected SC with saline (0.9% NaCl) solution or moxidectin SR at the rate of 0.06, 0.17, or 0.5 mg/kg of body weight (day 0). Each dog was inoculated SC with 50 D immitis L3 180 days later. On days 330 and 331, dogs were euthanatized. The heart, lungs, and thoracic cavity were examined, and number and sex of heartworms were determined.

RESULTS

A mean of 35.9 heartworms was recovered from untreated control dogs. Fourteen worms were recovered from 1 of 8 dogs given moxidectin SR at the lowest dosage, and none of the dogs in the 2 highest moxidectin treatment groups were infected. Small barely palpable granulomas were detected at injection sites of moxidectin-treated dogs. Frequency and size of granulomas were positively correlated with dose of moxidectin administered.

CONCLUSIONS AND CLINICAL RELEVANCE

A single dose of moxidectin SR at a dosage as low as 0.17 mg/kg can safely and reliably confer complete protection against infection after challenge-exposure with D. immitis L3, and protection lasts for at least 180 days. This mode of prophylactic treatment against infection with heartworms effectively eliminates failure of prophylaxis that results from erratic administration of medications designed for monthly administration.

Feline Hodgkin's-like lymphoma: 20 cases (1992-1999)

We identified 20 cases of feline lymphadenopathy that conform to many clinical and histologic manifestations of human Hodgkin's disease. Histologic subtypes encountered included lymphocyte predominance (nine cases), mixed cellularity (nine cases), and nodular sclerosis (two cases). Two cases were not easily classified; fibrous bands were present, but the absence of nodules supported a subclassification of mixed cellularity Hodgkin's disease. Immunohistochemical staining of the tissues using antibodies against the pan T-cell antigen CD3, the human B-lymphocyte antigen 36 (BLA.36), the pan B-lymphocyte and plasma cell marker CD79a, and a myeloid antigen (MAC387) confirmed the phenotypic heterogeneity of the tumor. Classic Reed-Sternberg (RS) cells and mononuclear, multinucleate, and lacunar cell variants did not stain with any of the antibodies used. In contrast, lymphohistiocytic RS variants (L+H cells) reacted positively to BLA.36 and CD79a B-cell markers. Eighteen of 20 affected cats were > or = 6 years of age (range, 1-14 years). A sex predilection could not be identified. These findings support the existence of Hodgkin's-like lymphoma in the cat. Proper identification of this disease in the cat will enable further characterization of clinical features and biologic behavior to determine whether there are significant differences in the treatment and prognosis of feline Hodgkin's-like lymphoma compared with non-Hodgkin's lymphoma.

Sensitivity and specificity of methods of assessing the regional lymph nodes for evidence of metastasis in dogs and cats with solid tumors

OBJECTIVE

To determine sensitivity and specificity of physical examination, fine-needle aspiration, and needle core biopsy of the regional lymph nodes for evidence of metastasis in dogs and cats with solid tumors.

DESIGN

Case series.

ANIMALS

37 dogs and 7 cats.

PROCEDURE

Regional lymph nodes were evaluated by means of physical examination (palpation), fine-needle aspiration, and needle core biopsy. Results were compared with results of histologic examination of the entire lymph node, the current standard.

RESULTS

Tumors included 18 sarcomas, 16 carcinomas, 7 mast cell tumors, and 3 other tumors. Carcinomas were more likely to have metastasized to the regional lymph node (7/16 animals) than were sarcomas (2/18). Sensitivity and specificity of physical examination were 60 and 72%, respectively. Sensitivity and specificity of cytologic examination of fine-needle aspirates were 100 and 96%, respectively. Sensitivity and specificity of histologic examination of needle core biopsy specimens were 64 and 96%, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that fine-needle aspiration may be a sensitive and specific method of evaluating the regional lymph nodes in dogs and cats with solid tumors, because results correlated well with results of histologic examination of the entire lymph node. Physical examination alone was not a reliable method and should not be used to decide whether to aspirate or biopsy the regional lymph nodes.

Clinical and pathologic aspects of spontaneous canine prostate carcinoma: a retrospective analysis of 76 cases

BACKGROUND

Pet dogs and men share a vulnerability for the development of prostate carcinoma. The purpose of this study was to further characterize the clinical and pathologic features of spontaneous canine prostate carcinoma.

METHODS

A multiinstitutional, retrospective study was conducted using 76 dogs with prostate carcinoma that underwent postmortem evaluation. For each case, clinical and pathologic data were tabulated and hematoxylin/eosin-stained tissue sections from the primary tumor and metastatic lesions were evaluated. Prostatic carcinomas were subclassified based upon the presence of glandular, urothelial, squamoid, or sarcomatoid differentiation. We focused our analysis on dogs that differed with respect to morphologic features of the primary tumor, lifetime duration of testicular hormone exposure, and presence of skeletal metastases.

RESULTS

The vast majority of canine prostate carcinomas affected elderly sexually intact dogs or dogs that underwent surgical castration after sexual maturity. Adenocarcinoma was the most frequent histologic type, although more than half of canine prostate carcinomas exhibited intratumoral heterogeneity. In many cases, primary tumors showed mixed morphology, characterized by two or more types of differentiation. Duration of testicular hormone exposure was significantly different between dogs with adenocarcinoma and dogs with mixed morphology tumor, but did not appear to influence the frequency or pattern of metastases. Overall, gross metastases were present in 80% of dogs with prostate carcinoma. Skeletal metastases were present in 22% of cases, and the predominantly axial skeletal distribution of these lesions was similar to that reported in men with prostate carcinoma. Young dogs were at highest risk for development of skeletal metastases.

CONCLUSIONS

This study provides a more complete characterization of spontaneous prostate carcinoma of dogs in terms of morphologic heterogeneity, skeletal metastases, and the influence of testicular hormones. Prostate carcinoma in pet dogs provides an immunocompetent, autochthonous tumor system that mimics certain aspects of human prostate cancer. This spontaneous model may contribute to our understanding of the factors that regulate carcinogenesis within the aged prostate, and to the development of chemoprevention strategies or bone-targeted therapies.

Prognosis for presumed feline vaccine-associated sarcoma after excision: 61 cases (1986-1996)

OBJECTIVE

To evaluate time to first recurrence (TFR) and overall survival in cats with presumed vaccine-associated sarcomas (VAS) treated with excision.

DESIGN

Retrospective study.

ANIMALS

61 cats with presumed VAS.

PROCEDURE

Medical records of cats that received excision as the only initial treatment for presumed VAS were reviewed to evaluate prognosis. Overall survival curves and TFR were determined.

RESULTS

Median TFR was 94 days. Median TFR for tumors treated with excision performed at a referral institution (274 days) was significantly longer than that for tumors excised by a referring veterinarian (66 days). Radical first excision yielded significantly longer median TFR (325 days) than did marginal first excision (79 days). Cats with tumors located on the limbs had longer median TFR (325 days) than cats with tumors located in other sites (66 days). Median overall survival time was 576 days. Significant differences in survival times between groups were not detected. Few cats (13.8%) receiving only surgical treatment had long-term (> 2 years) survival.

CONCLUSIONS AND CLINICAL RELEVANCE

Radical first excision of presumed VAS is essential for extended TFR. Current recommendations for vaccination of the distal portions of the extremities are appropriate, because this practice permits radical excision of tumors (amputation) that develop at vaccination sites; however, surgery alone is seldom curative.

Radiographic, ultrasonographic, and endoscopic findings in cats with inflammatory bowel disease of the stomach and small intestine: 33 cases (1990-1997)

OBJECTIVE

To characterize imaging findings in cats with confirmed inflammatory bowel disease (IBD) of the upper gastrointestinal tract (i.e., stomach and small intestine) and relate these findings to clinical signs and histologic changes.

DESIGN

Retrospective study.

ANIMALS

32 cats with clinical and histopathologic diagnoses of IBD.

PROCEDURE

Medical records were reviewed for signalment, clinical signs, clinicopathologic findings, radiographic and ultrasonographic findings, and results of endoscopic examination. Histologic findings were reviewed and characterized by severity and type of inflammatory infiltrate.

RESULTS

All cats had 1 or more clinical signs (e.g., vomiting, diarrhea, weight loss, and anorexia) consistent with IBD. Lymphocytic and plasmacytic infiltrates were observed in histologic sections of gastrointestinal tissue. Crypt distortion, villous blunting and fusion, and fibrosis were most commonly seen in cats with moderate or severe IBD. Clinicopathologic findings of some cats included anemia, leukocytosis or leukopenia, hypocholesterolemia, and hyper- or hypoproteinemia. Abnormalities were not found on abdominal radiographic views in 9 of 9 cats. However, contrast studies using barium revealed radiographic abnormalities in 1 of 3 cats. In 13 of 17 cats, abdominal ultrasonography revealed several intestinal abnormalities (e.g., poor intestinal wall layer definition, focal thickening) and large mesenteric lymph nodes with hypoechoic changes consistent with IBD. Endoscopic observation revealed findings (e.g., erythema, plaques, mucosal friability) consistent with inflammation in 9 of 18 cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Compared with endoscopy of the gastrointestinal tract or abdominal radiography, clinical signs and ultrasonographic findings appear to have the best association with histologic grade of IBD in cats.

Copper associated acute hepatic failure in a dog

A 1.5-year-old Dalmatian was examined because of vomiting, weight loss, and high serum activities of alanine aminotransferase and aspartate aminotransferase. Abdominal ultrasonography revealed normal appearing hepatic structure with echogenicity, but histologic examination of hepatic biopsy specimens revealed extensive necrosis of hepatocytes involving the centrilobular areas. Macrophages and remaining hepatocytes contained pigments that were positive for copper by rubeanic acid-staining and hepatic copper concentration was high. The dog was treated with crystalloid fluids, antibiotics, and a low copper diet; its condition deteriorated, and the dog was euthanatized. Primary copper storage disease was suspected on the basis of histologic findings and high copper concentration in the liver.

Malignant fibrous histiocytoma and malignant histiocytosis in the dog--convergent or divergent phenotypic differentiation?

Malignant fibrous histiocytoma (MFH) and malignant histiocytosis (MH) are neoplasms with different histologic appearances and consequently a different putative cell of origin. Recently, the biopsy and necropsy services at the University of Pennsylvania have seen many canine soft tissue sarcomas that have the gross and histologic appearances of both MH and MFH within the same animal. A retrospective histologic evaluation of 263 cases diagnosed originally as either MH or MFH reclassified these neoplasms into 77 cases that were exclusively MH, 110 cases exclusively MFH, and 76 cases with features of both MH and MFH. Age, sex, breed predispositions, and distribution of lesions in organs were remarkably similar between the two categories. The hybrid neoplasms containing MH-like and MFH-like regions may be the result of divergent or convergent phenotypic differentiation.

An uncommon intestinal manifestation of feline infectious peritonitis: 26 cases (1986-1993)

OBJECTIVE

To provide information on an uncommon intestinal manifestation of feline infectious peritonitis (FIP).

DESIGN

Retrospective case series.

ANIMALS

26 cats with FIP that had apparently solitary mural intestinal lesions.

PROCEDURE

Histologic records of cats for which FIP had been diagnosed by examination of the surgical biopsy specimens were reviewed. Slides of tissue samples from cats identified in the histologic record as having had intestinal lesions were reviewed by the investigators, and records of cats that appeared to have had solitary mural intestinal lesions were included in the study. Information including signalment; history; physical examination findings; results of hematologic, serum biochemical, and serologic analyses; findings at surgery; and results of histologic examination of biopsy specimens were retrieved from these records and supplemented by medical records and additional information obtained from veterinarians submitting the biopsy samples. ABC immunoperoxidase staining was used to detect FIP virus antigen in tissues from cats whose records were selected for inclusion in the study.

RESULTS

26 of 156 cats with a histologic diagnosis of FIP had apparently solitary mural intestinal lesions. Predominant clinical signs were diarrhea and vomiting for 3 months or less before biopsy. All cats had a mass, believed to be a neoplasm, in the colon or ileocecocolic junction. Affected intestine was markedly thickened, nodular, firm, and white, with multifocal pyogranulomas extending throughout the wall of the intestine on histologic examination. Associated lymph nodes were large. Results of immunohistochemical staining were positive for FIP virus. Most cats were euthanatized or died within 9 months of histologic results, many with signs of multisystemic FIP.

CLINICAL IMPLICATIONS

The apparent focal nature of intestinal lesions at surgery leads to a different clinical picture than usually seen with FIP, and masses often are believed to be neoplasms. Diagnosis of FIP is important to prevent exposure and infection of other cats. Evaluation of the entire abdominal cavity, biopsy of visible lesions as well as surrounding organs, and postmortem examination are recommended.

Radiographic findings in cats with intranasal neoplasia or chronic rhinitis: 29 cases (1982-1988)

OBJECTIVE

To compare radiographic findings and determine useful criteria to differentiate between intranasal neoplasia and chronic rhinitis in cats.

DESIGN

Retrospective study.

ANIMALS

Cats with chronic nasal disease caused by neoplasia (n = 18) or by chronic rhinitis (n = 11).

PROCEDURE

Radiographs were reviewed by 3 radiologists, followed by group review. Diagnosis was determined by intranasal biopsy or necropsy, and specimens were reviewed by a pathologist to confirm cause and histologic diagnosis.

RESULTS

Lymphosarcoma was the most common (n = 5) of the 6 histopathologic types in the neoplasia group. Cats in the neoplasia and chronic rhinitis groups had a high prevalence of aggressive radiographic lesions. Prevalence of a facial mass in cats with neoplasia (8/18) versus in those with chronic rhinitis (4/11) and of deviation (9/18 vs 6/11, respectively) or lysis (12/18 vs 7/11) of the nasal septum was similar. However, significantly (P = 0.02) more cats with neoplasia than with chronic rhinitis (13/16 vs 3/7, respectively) had unilateral turbinate destruction/lysis. Additionally, unilateral lateral bone erosion and loss of teeth associated with adjacent intranasal disease were more prevalent in cats with neoplasia (7/8 and 5/18, respectively) than in cats with chronic rhinitis (1/3 and 0/11, respectively).

CLINICAL IMPLICATIONS

Features that may assist in radiographic diagnosis of neoplasia include the appearance of unilateral aggressive lesions, such as lysis of lateral bones, nasal turbinate destruction, and loss of teeth. Bilaterally symmetric lesions are more suggestive of chronic rhinitis than of neoplasia.

The potential role of inflammation in the development of postvaccinal sarcomas in cats

Epidemiologic evidence shows a strong association between the administration of inactivated feline vaccines (feline leukemia virus and rabies) and subsequent soft tissue sarcoma development at vaccine sites. Although more research is needed to understand the complete pathogenesis of vaccine-induced tumors in cats, good evidence exists that inflammation plays a role.

Comparison of fibrosarcomas that developed at vaccination sites and at nonvaccination sites in cats: 239 cases (1991-1992)

Questionnaires were sent to veterinarians who had submitted a fibrosarcoma from a cat to the surgical pathology services of the veterinary schools of the University of Pennsylvania and Tufts University between Jan 1, 1991 and June 30, 1992. Questionnaire items included signalment, FeLV and feline immunodeficiency virus status, site of sarcoma, vaccination site, vaccines used, treatment, biologic behavior of the tumor, and final outcome. Data were analyzed, using Student's t-test for continuous data, chi 2 test for categoric data, and log-rank test for survival estimates. Comparing results for cats with vaccination-site (VS) tumors and nonvaccination-site (NVS) tumors, we determined that VS tumors developed in younger cats and were larger than NVS tumors. Although VS sarcomas were biologically aggressive and redeveloped more often than NVS sarcomas, metastasis was not detected, and cats with VS tumors survived longer than cats with NVS tumors. Vaccination-site sarcomas developed in cats after injection of many types of vaccines, administered singularly or in combination. Of the cats in the VS group administered a single vaccine, 37% were given rabies, 33% were given feline viral rhinotracheitis/calicivirus/panleukopenia virus, and 30% were given FeLV vaccines. Cats with VS tumors were more likely to have received FeLV vaccine and less likely to have received rabies vaccine than those with NVS tumors. Although vaccines produced by certain manufacturers were used most often in cats with VS and NVS sarcomas, it was believed that this probably represented marketing practices and brand popularity.(ABSTRACT TRUNCATED AT 250 WORDS)

Granulomatous hepatitis in dogs: nine cases (1987-1990)

Granulomatous hepatitis (GH) is an uncommon histopathologic diagnosis in dogs. On the basis of clinical reports, fungal infections appear to be the most common cause of GH in dogs, but many other potential causes have been identified. The medical records and histopathologic findings for 9 dogs with GH were reviewed to identify additional specific causes of GH in dogs. Diseases associated with GH included intestinal lymphangiectasia (n = 2), lymphosarcoma (n = 1), histiocytosis (n = 1), dirofilariasis (n = 1), and histoplasmosis (n = 1). In 1 dog, no other disease process was identified. Of the remaining 2 dogs, 1 had concurrent granulomatous pneumonitis of unknown cause, and the other had periportal hepatitis and temporal muscle wasting. All 9 dogs with GH had clinical evidence of liver disease, such as hepatomegaly, icterus, and ascites, or had high serum alkaline phosphatase and alanine aminotransferase activity. Because of the wide variety of potential causes of GH in dogs, an accurate diagnosis should be sought so that appropriate treatment can be chosen and an accurate prognosis given.

Acute pancreatitis in cats with hepatic lipidosis

The purpose of this study was to characterize the incidence, clinical features, and prognosis of acute pancreatitis in cats with hepatic lipidosis. Of 13 cats histologically diagnosed with hepatic lipidosis between July 1988, and November 1989, 5(38%) were also histologically diagnosed with acute pancreatitis. In cats with hepatic lipidosis alone, the signalment, history, physical examination, and clinicopathologic findings were generally indistinguishable from those of cats with concurrent acute pancreatitis except that cats with acute pancreatitis were more likely to be cachectic and to have coagulation abnormalities. Hepatomegaly was seen on abdominal radiographs in both groups. Of the 5 cats with concurrent acute pancreatitis, abdominal ultrasonography detected 1 cat with a hypoechoic pancreas and 5 with peritoneal effusion; those abnormalities were not seen in cats without concurrent acute pancreatitis. Cats with concurrent acute pancreatitis had only a 20% recovery rate, compared with a 50% recovery rate in cats with hepatic lipidosis alone. We conclude that cats with hepatic lipidosis should be rigorously evaluated for concurrent acute pancreatitis because of 1) the rate of disease coincidence, 2) the inability of signalment, history, physical examination, and clinicopathologic findings to adequately distinguish between hepatic lipidosis and acute pancreatitis, 3) the worse prognosis associated with concurrent acute pancreatitis, and 4) the opposing nutritional strategies for hepatic lipidosis and acute pancreatitis.

Postvaccinal sarcomas in the cat: epidemiology and electron probe microanalytical identification of aluminum

An increase in fibrosarcomas in a biopsy population of cats in the Pennsylvania area appears to be related to the increased vaccination of cats following enactment of a mandatory rabies vaccination law. The majority of fibrosarcomas arose in sites routinely used by veterinarians for vaccination, and 42 of 198 tumors were surrounded by lymphocytes and macrophages containing foreign material identical to that previously described in postvaccinal inflammatory injection site reactions. Some of the vaccines used have aluminum-based adjuvants, and macrophages surrounding three tumors contained aluminum oxide identified by electron probe microanalysis and imaged by energy-filtered electron microscopy. Persistence of inflammatory and immunological reactions associated with aluminum may predispose the cat to a derangement of its fibrous connective tissue repair response, leading to neoplasia.

Pathological and radiographical features of multicentric malignant fibrous histiocytoma in two dogs

Widespread organ distribution of malignant fibrous histiocytoma, including osseous involvement, was demonstrated in two dogs. Both cases had a storiform-pleomorphic pattern histologically and immunohistochemical stains were used to differentiate this from other types of neoplasms with the same histological pattern. Radiographically the lesions were predominantly lytic in the metaphysis of long bones, although periosteal proliferation and axial skeletal involvement were seen in one dog.

Focal necrotizing granulomatous panniculitis associated with subcutaneous injection of rabies vaccine in cats and dogs: 10 cases (1988-1989)

Twenty-three biopsy specimens were diagnosed as injection-site reactions by the Laboratory of Pathology of the University of Pennsylvania between September 14, 1988 and June 26, 1989. Historical information about 10 animals from which biopsy specimens were obtained was acquired through written questionnaires sent to veterinarians. Eight cats and 2 dogs had been injected in the subcutis with rabies vaccine or rabies vaccine combined with other vaccines approximately 2 weeks to 2 months prior to appearance of the lesion. All lesions were well-circumscribed, firm, subcutaneous masses that had a zone of central necrosis, with peripheral infiltration by macrophages, and variable numbers of lymphocytes, plasma cells, and eosinophils. Although most biopsy lesions sites healed after a few weeks, intramuscular rabies vaccination seems preferable until a less pathogenic, subcutaneously administered vaccine is available.

Retained caseous yolk sac in a Burmese python (Python molurus bivittatus)

Retained yolk sacs are common in the domestic chicken and account for considerable morbidity and mortality during late embryonic development and within the first 10 days of life. What is believed to be the first recorded instance of a retained caseous yolk sac and its successful surgical removal from a Burmese python (Python molurus bivittatus) is reported. The snake experienced no post-operative complications and continues to be well 16 mo following surgery.

Macrohematuria and life-threatening anemia attributable to subepithelial vascular ectasia of the urinary bladder in a dog

Hematuria leading to life-threatening anemia was evaluated in a 9-year-old male dog. At surgery, an abnormal vessel resembling an ulcerated varicose vein was found on the surface of the bladder mucosa. After removal of the lesion, hematuria ceased and had not recurred 22 months later.

Orthovoltage radiotherapy of primary lymphoma of bone in a dog

A 1 1/2-year-old castrated Boxer with a progressive left forelimb lameness of 1 month's duration had a solitary immunoblastic B-cell lymphoma of the proximal portion of the ulna. This primary lymphoma of bone was successively treated with orthovoltage radiation (45 Gy divided into 10 fractions over 22 days). The dog gradually regained normal gait function and did not develop any local recurrence over 34 months. In dogs, primary lymphoma of bone is a rare primary bone tumor, and the ulna is an unusual location for extranodal lymphoma. Local administration of radiation appears to be an effective treatment, allowing retention of normal function.