What Is Your Diagnosis?

Jeanne Marie Gaughan Longwood Veterinary Center, 230 Kennett Pike, Kennett Square, PA 19348 and the Veterinary Specialty Center of Delaware, 1212 E Newport Pike, Wilmington, DE 19804.

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A 10-year-old 15.3-kg (33.7-lb) spayed female mixed-breed dog was evaluated for a non–weight-bearing lameness of the left thoracic limb of 1 week's duration. The client had intermittently administered ibuprofen orally for the lameness. On physical examination, the left and right mandibular lymph nodes and the right superficial cervical lymph node were large and the popliteal lymph nodes were firm bilaterally. The left carpal joint was swollen, and palpation of the joint elicited signs of pain. Splenomegaly was detected during abdominal palpation.

Abnormalities detected on CBC included mild anemia (Hct, 33.5%; reference range, 36% to 60%) and leukocytosis (18.5 × 103 cells/μL; reference range, 4.0 to 5.5 × 103 cells/μL) with a mature neutrophilia (78%). High alkaline phosphatase activity (213 U/L; reference range, 5 to 131 U/L) was the only abnormality detected on serum biochemical analyses. Samples of fine-needle aspirates obtained from the right superficial cervical and right mandibular lymph nodes were submitted for cytologic examination. Synovial fluid samples obtained during arthrocentesis of the left antebrachiocarpal joint were submitted for cytologic examination, fluid analysis, and bacterial culture.

Initial differential diagnoses included infectious disease (eg, septic arthritis with bacterial origin, rickettsial disease, or fungal disease), inflammatory disease, immune-mediated disease (eg, rheumatoid arthritis or systemic lupus erythematosus), neoplasia (most likely synovial cell sarcoma), or trauma. Radiographic views of the thorax and abdomen were obtained to evaluate for thoracic metastasis and abdominal organomegaly. Radiographic views of the left carpal joint were obtained to identify possible causes of the left thoracic limb lameness (Figure 1).

Figure 1—
Figure 1—

Dorsopalmar (A) and lateromedial (B) radiographic views of the left carpus of a 10-year-old mixed-breed dog evaluated for non–weight-bearing lameness of the left thoracic limb of 1 week's duration.

Citation: Journal of the American Veterinary Medical Association 231, 2; 10.2460/javma.231.2.203

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page

Radiographic Findings and Interpretation

The periarticular tissues of the left carpus are swollen diffusely (Figure 2). On the dorsopalmar radiographic view, the opacity of the first and second carpal bones is diminished, compared with the other carpal bones. Along the dorsal surfaces of the small carpal bones, there is evidence of periosteal changes. An enthesophyte is evident on the lateral aspect of the base of the fifth metacarpal bone.

Figure 2—
Figure 2—

Same radiographic views as in Figure 1. On the dorsopalmar radiographic view (A), the opacity of the first and second carpal bones is diminished (arrow), compared with the other carpal bones. On the lateromedial radiographic view (B), the tissues of the left carpus are swollen (arrow).

Citation: Journal of the American Veterinary Medical Association 231, 2; 10.2460/javma.231.2.203

Differential diagnoses for the radiographic findings included infection as the most likely possibility (eg, septic arthritis with osteomyelitis), immune-mediated arthritis, and neoplasia. Enthesophytes are commonly associated with collateral ligament attachments and are considered a chronic change. In the dog of this report, it was the least likely cause for the lameness. Thus, non–weight-bearing lameness of the left thoracic limb was attributed to an erosive arthropathy of the left carpal joint with diffuse swelling.


Each lymph node aspirate contained abundant lymphoblasts. No infectious agents were detected during cytologic examination of synovial fluid and no growth was detected on bacteriologic culture of the joint fluid. The preponderance of lymphoblasts within the synovial fluid resulted in a diagnosis of lymphoma within the carpal joint. Secondary inflammation was also detected and was likely attributable to the tumor infiltration. Because an infectious process, synovial cell sarcoma, or immune-mediated disease was suspected, a diagnosis of lymphoma within the joint was an unexpected finding. The client declined further diagnostic testing and chemotherapy and chose to treat the dog with prednisone only. Intermittent administration of ibuprofen was discontinued. Five months after initial diagnosis, the dog was still alive.

During inflammation, lymphocytes can undergo a blastic or immunoreactive transformation1 and should not be overinterpreted during cytologic examination of synovial fluid. In the dog reported here, the large overall number of lymphoblasts (> 2,000/μL, > 10% of the total nucleated cell count) and results of cytologic examination of peripheral lymph node aspirates confirmed a diagnosis of lymphoma. Further diagnostic evaluation of lymph nodes or joint fluid may have included immunophenotype staining to specify T-versus β-cell origin of the lymphoma, which provides prognostic information.2 Abdominal ultrasonography and histologic examination of synovium biopsy and bone marrow biopsy specimens may also be considered for staging and diagnostic purposes.

To the author's knowledge, only 1 case of T-cell lymphoma of the synovium in a dog has been reported.3 In humans, synovial lymphoma is not commonly reported.4–7 The human literature documented that lymphoma is often misdiagnosed when a joint is the first symptomatic location.8,9,a Radiographic evidence of associated bone destruction is the best evidence for non-Hodgkin's lymphomatous arthropathy in humans with rheumatic symptoms; however, the absence of radiographic findings does not exclude a diagnosis of lymphoma.10 Other diagnostic tests, even minimally invasive techniques such as arthrocentesis, should also be performed and can yield substantial findings in humans with joint effusion.7,9,10 Interestingly, the dog reported here also had radiographic evidence of bone lysis within certain carpal bones of the affected joint, and a diagnosis of lymphoma was confirmed via cytologic examination of synovial fluid aspirates. Although rare, lymphoma should be included as a differential diagnosis in dogs with joint swelling, lymphadenopathy, and radiographic evidence of bony changes.


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    Peeva E, Davidson A, Keiser HD. Synovial non-Hodgkin's lymphoma in a human immunodeficiency virus infected patient. J Rheumatol 1999;26:696698.

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    Mariette X, deRoquancourt A & d'Agay MF, et al. Monoarthritis revealing non-Hodgkin's T-cell lymphoma of the synovium. Arthritis Rheum 1988;31:571572.

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    Adunsky A, Yaretzky A, Klajman A. Malignant lymphoma presenting as sternoclavicular joint arthritis. Arthritis Rheum 1980;23:13301331.

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    Emkey RD, Ragsdale BD & Ropes MW, et al. A case of lymphoproliferative disease presenting as juvenile rheumatoid arthritis, diagnosis by synovial fluid examination. Am J Med 1973;54:825828.

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  • 10

    Dorfman HD, Siegel HL & Perry MC, et al. Non-Hodgkin's lymphoma of the synovium simulating rheumatoid arthritis. Arthritis Rheum 1987;30:155161.

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