What Is Your Diagnosis?

Megan M. Templeton Dallas Veterinary Surgical Center, 4444 Trinity Mills Rd, Ste 203, Dallas, TX 75287.

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H. Fulton Reaugh Dallas Veterinary Surgical Center, 4444 Trinity Mills Rd, Ste 203, Dallas, TX 75287.

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History

A 9-year-old neutered male Labrador Retriever was referred for evaluation of labored breathing of 30 minutes' duration. Pertinent medical history included administration of monthly heartworm preventative, no history of a known traumatic event, and no previous respiratory signs, including cough, dyspnea, or exercise intolerance. The patient had not been anesthetized within the previous year. On evaluation, the patient was sternally recumbent with a substantial increase in respiratory effort and high respiratory rate (> 70 breaths/min). The patient was tachycardic (156 beats/min) with no murmurs or arrhythmias detected on auscultation and moderate, synchronous femoral pulses. Thoracic auscultation revealed harsh lung sounds along the right hemithorax and slightly muffled cardiac and lung sounds in the left mid to ventral hemithorax. The remainder of the physical examination was unremarkable. Serum biochemical analysis revealed no abnormalities. Complete blood count was not available, but PCV was low (26%; reference range, 37% to 55%) with a total solids concentration within reference range (7.2 mg/dL; reference range, 6 to 9 mg/dL). Oxygen saturation of hemoglobin as measured by pulse oximetry was 87% while breathing room air, with mild improvement (93%) when oxygen was administered via face mask at a flow of 3 L/min. Thoracic radiographs were obtained (Figure 1).

Figure 1—
Figure 1—

Right lateral (A) and ventrodorsal (B) radiographic views of the thorax of a 9-year-old neutered male Labrador Retriever evaluated for acute onset of labored breathing.

Citation: Journal of the American Veterinary Medical Association 239, 7; 10.2460/javma.239.7.927

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

Radiographic Findings and Interpretation

On the lateral projection, there is scalloping of the cranial and caudal lung fields along the ventral borders (Figure 2). A soft tissue opacity is present, most likely within the pleural space, which silhouettes with the ventral border of the heart and diaphragm. The remainder of the aerated pulmonary parenchyma has a mild generalized increase in opacity consistent with superimposed fluid or underlying pulmonary disease. Retraction of the right caudal lung lobe is noted on the ventrodorsal view with pleural fissure lines present between the right cranial and right middle lung lobes.

Figure 2—
Figure 2—

Same radiographic views as in Figure 1. A—On the lateral view, notice the scalloping of the edges of the lung lobes (white arrows), solitary osteolytic and proliferative lesion of the left fifth rib (black arrowheads), and caudal margin of a band of soft tissue opacity at the level of the fourth and sixth intercostal spaces (white arrowheads). B—On the ventrodorsal view, notice the pleural fissure lines between the right cranial and middle lung lobes (black arrows), the solitary osteolytic and proliferative lesion of the left fifth rib (black arrowheads), and the broad-based, triangular-shaped soft tissue opacity at the level of the fourth and sixth left intercostal spaces (white arrowheads).

Citation: Journal of the American Veterinary Medical Association 239, 7; 10.2460/javma.239.7.927

Along the fifth rib in the left hemithorax, severe periosteal reaction with lobulated and indistinct margins is noted along with a solitary osteolytic lesion on both radiographic views (Figures 2). On the ventrodorsal view, a triangular-shaped soft tissue opacity based broadly along the body wall is present at the level of the fourth and sixth intercostal spaces on the left. On the lateral view, this is seen as a band of soft tissue superimposed over the heart centered over the affected rib with a well-delineated caudal border.

Radiographic diagnoses included a solitary osteolytic and proliferative mass originating from the left fifth rib, possible pulmonary mass in the caudal segment of the left cranial lung lobe, or soft tissue mass associated with the rib lesion and secondary pleural effusion. Primary differential diagnoses included rib neoplasia versus pleural neoplasia, abscess, or granuloma. Although much less likely, a lung lobe torsion and primary pulmonary neoplasia could be considered as differential diagnoses.1

Comments

A left lateral thoracotomy at the level of the fourth to fifth intercostal space was performed, and a large, hemorrhaging mass that was attached to the fifth rib was encountered. There was approximately 1 L of hemorrhagic fluid within the thoracic cavity. The fifth rib was resected and submitted for histologic examination. The patient received a transfusion of 1 U of whole blood intraoperatively, and a chest tube was placed. After surgery, the patient was maintained on a constant rate infusion of fentanyl and medetomidine. Thoracic fluid production gradually decreased over 3 days, and the patient was discharged from the hospital 4 days after surgery with a good appetite, normal findings on thoracic auscultation, and stable PCV of 31%.

Histologic examination of the rib mass revealed a probable plasma cell tumor. Plasma cell neoplasms arise from the B-lymphocytic cell lineage and cause many clinical syndromes, including multiple myeloma, IgM macro-globulinemia, and solitary plasmacytomas.2

Solitary plasmacytomas can occur as either extramedullary (soft tissue) or single osseous plasmacytomas and, in 1 study,3 represented 2.4% of all tumors in dogs. Osseous plasmacytomas reflect neoplastic proliferation of plasma cells within the bone marrow cavity. They most commonly affect the flat bones of the head, the vertebrae, ribs, pelvis, and the proximal ends of the femur and humerus. Clinical signs are variable and can manifest as either orthopedic or neurologic disease, depending on the location of the lesions. Radiographically, this disease, like most osseous tumors, causes some evidence of osteolysis. This osteolysis can be isolated in the case of a solitary lesion or can manifest as diffuse osteopenia in cases of multiple myeloma where the diffuse marrow involvement results in loss of bone trabeculae and thinning of the bone cortices.4 Unfortunately, most cases of single osseous plasmacytoma eventually progress to systemic multiple myeloma, but the time course from local tumor development to systemic disease may be many months to years.5

  • 1.

    Root CR, Bahr RJ. The thoracic wall. In: Thrall DE, eds. Textbook of veterinary diagnostic radiology. 4th ed. Philadelphia: WB Saunders Co, 2002;351357.

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  • 2.

    Vail DM. Plasma cell neoplasms. In: Withrow SJ, Vail DM, eds. Withrow and MacEwen's small animal clinical oncology. 4th ed. St Louis: Saunders Co, 2006;779784.

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    • Export Citation
  • 3.

    Kupanoff PA, Popovitch CA, Goldschmidt MH. Colorectal plasmacytomas: a retrospective study of nine dogs. J Am Anim Hosp Assoc 1994; 204: 12101211.

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    • Export Citation
  • 4.

    MacEwen EG, Hurvitz AL. Diagnosis and management of monoclonal gammopathies. Vet Clin North Am Anim Pract 1977; 7: 119132.

  • 5.

    Meis JM, Butler JJ, Osborne BM, et al. Solitary plasmacytomas of bone and extramedullary plasmacytomas. Cancer 1987; 59: 14751485.

    • Crossref
    • Search Google Scholar
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  • Figure 1—

    Right lateral (A) and ventrodorsal (B) radiographic views of the thorax of a 9-year-old neutered male Labrador Retriever evaluated for acute onset of labored breathing.

  • Figure 2—

    Same radiographic views as in Figure 1. A—On the lateral view, notice the scalloping of the edges of the lung lobes (white arrows), solitary osteolytic and proliferative lesion of the left fifth rib (black arrowheads), and caudal margin of a band of soft tissue opacity at the level of the fourth and sixth intercostal spaces (white arrowheads). B—On the ventrodorsal view, notice the pleural fissure lines between the right cranial and middle lung lobes (black arrows), the solitary osteolytic and proliferative lesion of the left fifth rib (black arrowheads), and the broad-based, triangular-shaped soft tissue opacity at the level of the fourth and sixth left intercostal spaces (white arrowheads).

  • 1.

    Root CR, Bahr RJ. The thoracic wall. In: Thrall DE, eds. Textbook of veterinary diagnostic radiology. 4th ed. Philadelphia: WB Saunders Co, 2002;351357.

    • Search Google Scholar
    • Export Citation
  • 2.

    Vail DM. Plasma cell neoplasms. In: Withrow SJ, Vail DM, eds. Withrow and MacEwen's small animal clinical oncology. 4th ed. St Louis: Saunders Co, 2006;779784.

    • Search Google Scholar
    • Export Citation
  • 3.

    Kupanoff PA, Popovitch CA, Goldschmidt MH. Colorectal plasmacytomas: a retrospective study of nine dogs. J Am Anim Hosp Assoc 1994; 204: 12101211.

    • Search Google Scholar
    • Export Citation
  • 4.

    MacEwen EG, Hurvitz AL. Diagnosis and management of monoclonal gammopathies. Vet Clin North Am Anim Pract 1977; 7: 119132.

  • 5.

    Meis JM, Butler JJ, Osborne BM, et al. Solitary plasmacytomas of bone and extramedullary plasmacytomas. Cancer 1987; 59: 14751485.

    • Crossref
    • Search Google Scholar
    • Export Citation

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