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Alexandre Le Roux Diagnostic Imaging Unit, Ecole Nationale Vétérinaire de Nantes, Atlanpole - La Chantrerie, BP 40706, 44307 Nantes Cedex 03, France.

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Michael Rabillard Small Animal Surgery Unit, Ecole Nationale Vétérinaire de Nantes, Atlanpole - La Chantrerie, BP 40706, 44307 Nantes Cedex 03, France.

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Olivier Gauthier Small Animal Surgery Unit, Ecole Nationale Vétérinaire de Nantes, Atlanpole - La Chantrerie, BP 40706, 44307 Nantes Cedex 03, France.

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Marion Fusellier Diagnostic Imaging Unit, Ecole Nationale Vétérinaire de Nantes, Atlanpole - La Chantrerie, BP 40706, 44307 Nantes Cedex 03, France.

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Olivier Albaric Veterinary Pathology Unit, Ecole Nationale Vétérinaire de Nantes, Atlanpole - La Chantrerie, BP 40706, 44307 Nantes Cedex 03, France.

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Jack-Yves Deschamps Small Animal Internal Medicine Unit, Ecole Nationale Vétérinaire de Nantes, Atlanpole - La Chantrerie, BP 40706, 44307 Nantes Cedex 03, France.

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History

A 5-year-old spayed female Boxer was referred for evaluation because of progressive abdominal distension over the preceding 2 months. The dog appeared depressed and was thin. On physical examination, several firm masses were palpated in the abdomen. Findings on orthopedic examination were unremarkable; there were no signs of lameness, pain, or limb swelling. A CBC and serum biochemical analysis revealed hyponatremia (120 mmol/L; reference range, 140 to 150 mmol/L) and mild hypocalcemia (88 mg/L; reference range, 92 to 108 mg/L). Radiographs of the abdomen were obtained (Figure 1).

Figure 1—
Figure 1—

Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 5-year-old spayed female Boxer that was evaluated because of progressive abdominal distension over the preceding 2 months.

Citation: Journal of the American Veterinary Medical Association 237, 11; 10.2460/javma.237.11.1241

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

Radiographic Findings and Interpretation

A large mass with a heterogeneous mineral opacity occupying the cranial and most of the middle portions of the abdomen is located immediately caudal to the diaphragm and ventral to the thoracolumbar vertebrae. The large mass has smooth margins cranially and ventrally, but its borders are irregular and difficult to delineate caudally. The liver, spleen, and stomach cannot be outlined on the images. Several well-defined radiopaque masses that have opacity similar to that of bone are evident in the cranioventral portion of the abdomen and appear to be mesenteric or hepatic parenchymal mineralizations. In addition, smooth circular masses with a homogenous mineral opacity are located in the caudoventral region of the abdomen and are indicative of ectopic mineralizations of the mesentery. There is a lack of serosal detail in the ventral portion of the abdomen, which is consistent with focal peritonitis, carcinomatosis, or abdominal effusion (Figure 2).

Figure 2—
Figure 2—

Same radiographic images as in Figure 1. Notice the large mass with a heterogeneous mineral opacity in the cranial and most of the middle portions of the abdomen (small white arrows). Hepatic or mesenteric mineralizations that have opacity similar to that of bone are evident in the cranioventral portion of the abdomen (black arrow). Smooth nodular radiopaque masses are located in the caudoventral region of the abdomen and are indicative of ectopic calcification of the mesentery (white arrowheads). The ventral portion of the abdomen lacks serosal detail.

Citation: Journal of the American Veterinary Medical Association 237, 11; 10.2460/javma.237.11.1241

Two-view thoracic radiography did not reveal any evidence of metastatic disease, as pulmonary nodules were not found. However, well-defined radiopaque masses were observed immediately caudal to the ventral part of the diaphragm, at the level of the costal arch in the hepatic projection area, and were consistent with hepatic parenchymal mineralization (Figure 3). Differential diagnoses for these mineralizations were neoplasia (eg, adenocarcinoma or osteosarcoma) of the liver, spleen, or stomach with generalization to the abdominal cavity or diseases that may lead to soft tissue mineralization.

Figure 3—
Figure 3—

Right lateral radiographic view of the thorax of the dog of this report. Multiple mineralized masses (black arrow) are evident in the hepatic projection area at the level of the costal arch and are consistent with hepatic mineralizations.

Citation: Journal of the American Veterinary Medical Association 237, 11; 10.2460/javma.237.11.1241

Comments

An exploratory laparotomy was performed, and abdominal effusion was observed. Many ossified masses and nodules were present on the mesentery, which was thickened and hardened. The left and caudate lobes of the liver had an appearance and a consistency similar to bone. The spleen and kidneys had a normal macroscopic appearance. Histologic examination of mesentery and liver tissue specimens revealed osteosarcoma, providing a diagnosis of hepatic extraskeletal osteosarcoma with secondary abdominal dissemination. The dog's owners declined further diagnostic testing and treatment. Three months after the diagnosis, the dog was euthanatized.

Ectopic calcification is classified as metastatic or dystrophic calcification. Metastatic calcification most often occurs when the calcium-phosphorus product exceeds 60 to 70 mg2/dL2. In the absence of systemic mineral imbalance, ectopic calcification is termed dystrophic calcification; often, these sites have evidence of tissue alteration and necrosis. The dog of this report had mild hypocalcemia and a serum phosphorus concentration within reference limits, indicating that calcifications in the abdomen were dystrophic.1

A diagnosis of extraskeletal osteosarcoma requires that the tumor originate in soft tissue and not be attached to bone or periosteum, have a uniform morphological pattern of sarcomatous tissue and a high mitotic index, and produce malignant osteoid or bone.2 The dog of this report had no history of swelling of the limbs or lameness, although a covert primary skeletal lesion involving the skull or an extremity could not be completely ruled out. Bone scintigraphy could have been performed in search of a primary bone lesion to further confirm extraskeletal osteosarcoma, but was not feasible for this dog given the grave prognosis.

  • 1.

    Lamb CR, Kleine LJ, McMillan MC. Diagnosis of calcification on abdominal radiographs. Vet Radiol 1991; 32:211-220.

  • 2.

    Patnaik AK. Canine extraskeletal osteosarcoma and chondrosarcoma: a clinicopathologic study of 14 cases. Vet Pathol 1990; 27:46-55.

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