History
A 13-year-old 20-kg (44-lb) neutered male mixed-breed dog was evaluated because of vomiting and anorexia of 5 days’ duration. Physical examination revealed that the dog was approximately 10% dehydrated. A firm, palpable mass was detected in the right cranial aspect of the abdomen. The dog had a body temperature of 40.2°C (104.4°F), respiratory rate of 80 breaths/min, and heart rate of 160 beats/min. A CBC revealed leukocytosis (38,300 leukocytes/μL; reference range, 5,000 to 17,000 leukocytes/μL), characterized by neutrophilia (31,023 neutrophils/μL; reference range, 3,000 to 11,400 neutrophils/μL) with a regenerative left shift (766 band neutrophils/μL; reference range, 0 to 300 band neutrophils/μL). Serum biochemical analysis revealed high activities of aspartate aminotransferase (233 U/L; reference range, 15 to 50 U/L), alanine transaminase (202 U/L; reference range, 15 to 90 U/L), and alkaline phosphatase (404 U/L; reference range, 10 to 110 U/L). Hyperphosphatemia (5.9 mg/dL; reference range, 2.7 to 5.6 mg/dL), hypocalcemia (8.5 mg/dL; reference range, 9.3 to 11.5 mg/dL), hypochloremia (108 mmol/L; reference range, 110 to 120 mmol/L), and hypoalbuminemia (2.2 g/dL; reference range, 2.5 to 3.8 g/dL) were also observed. Abdominal radiographs were obtained (Figure 1).
Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 13-year-old neutered male mixed-breed dog that was evaluated because of vomiting and anorexia of 5 days’ duration.
Citation: Journal of the American Veterinary Medical Association 246, 7; 10.2460/javma.246.7.733
Diagnostic Imaging Findings and Interpretation
In the right lateral and ventrodorsal radiographic images, decreased visualization of the serosal margins and a heterogeneous appearance to the falciform fat are indicative of effusion (Figure 2). There is a moderate to marked caudodorsal displacement of the gastric axis, and a small amount of gas within the stomach has been caudally displaced toward the left side of the body wall on the ventrodorsal image, supporting a mass effect originating from the right cranial aspect of the abdomen. The margins of the mass are poorly defined but appear to be lobulated on the lateral projection. The liver margins are also poorly defined. Another mass effect is visible in the midabdomen, where it laterally and caudally displaces the small intestines. The radiographic findings are most compatible with a mass in the right cranial aspect of the abdomen with abdominal effusion. Differential diagnoses for the mass in the cranial aspect of the abdomen included hepatic neoplasia (eg, adenocarcinoma, hepatobiliary carcinoma, hemangiosarcoma, hepatoma, and histiocytic sarcoma). Additional but less likely diagnoses included granuloma, cyst, or hematoma. Inflammation, lipidosis, steroid hepatopathy, or congestion were considered unlikely, given the predominantly right-sided involvement. Origination of the mass from the stomach could not be excluded on the basis of radiographic findings. The most likely differential diagnoses for the peritoneal effusion included paraneoplastic effusion, carcinomatosis, and hemorrhage. Other less likely diagnoses included peritonitis, hypoalbuminemia, and cardiovascular dysfunction. Alternative differential diagnoses for the mass effect in the midabdomen included regional lymphadenopathy or neoplasia, abscess, granuloma, or cyst associated with the mesentery or omentum.
Same radiographic images as in Figure 1. A—Notice the decreased serosal detail and the caudodorsal displacement of the gastric axis (arrowheads). A soft tissue mass effect can be seen in the midabdomen, and the small intestines are displaced caudally (arrows). B—Notice the left and caudal displacement of gastric gas (arrowheads) and the caudolateral displacement of the small intestines (arrows).
Citation: Journal of the American Veterinary Medical Association 246, 7; 10.2460/javma.246.7.733
Abdominal ultrasonography was performed to further characterize the mass in the cranial aspect of the abdomen, effusion, and mass effect (Figure 3). The liver size and margin were found to be within reference limits, but several hypoechoic nodules were observed in the liver. A large hyperechoic mass (> 10 cm in diameter) with irregular margins and multiple hypoechoic and poorly defined regions was observed; this mass occupied the cranial portion of the abdomen between the liver and the stomach. The gastric wall layering was completely lost in most of the pyloric region, but some layering appeared to be intact, despite muscularis layer thickening. The mass originated from the muscularis layer of the pyloric region of the stomach and extended caudally to the midabdomen, which was compatible with the mass effect that was radiographically visualized in the midabdomen. Multiple nodules of mixed echogenicity were found throughout the abdomen, along with a small amount of peritoneal effusion. The ultrasonographic findings were indicative of gastric neoplasia (eg, leiomyosarcoma, gastric stromal cell tumor, gastric carcinoma, or lymphoma) with peritoneal metastases.
Sagittal ultrasonographic images of the pyloric region of the stomach of the same dog as in Figure 1. A—Notice the heterogeneous and hyperechoic mass with irregular margins that is > 10 cm in diameter (arrows), with hypoechoic regions caudal to the liver. B—The gastric wall layering in the near field is intact, but the muscularis layer is thickened. Notice the mass in the pyloric muscularis layer (arrowheads) and the gas in the pyloric lumen (arrow). Scales on the left indicate length in centimeters. GB = Gallbladder.
Citation: Journal of the American Veterinary Medical Association 246, 7; 10.2460/javma.246.7.733
Treatment and Outcome
Ultrasound-guided fine-needle aspiration of the gastric masses and peritoneal nodules was performed. Cytologic evaluation of the aspirates resulted in a diagnosis of suspected sarcoma. Owing to the poor prognosis, the owners decided to euthanize the dog. During necropsy, origin of the mass from the muscularis layer of the pyloric region of the stomach was confirmed. Multifocal purplish red nodules of various sizes were disseminated in the greater omentum. The histopathologic diagnosis made from evaluation of the gastric mass was a gastrointestinal stromal tumor (GIST) with metastases in the liver and omentum.
Comments
Gastrointestinal tumors account for approximately 3% of all canine neoplasms.1 Gastrointestinal stromal tumors are common mesenchymal tumors in humans, but not in dogs. However, GISTs might not be as uncommon as previously thought, given that many previously diagnosed leiomyosarcomas have been immunohistochemically reclassified as GISTs.1 Gastrointestinal stromal tumor diagnosis relies on the histologic detection of CD117 (c-kit) expression and uses immunohistochemistry to differentiate GISTs from gastric leiomyosarcomas.1 Compared with small intestines and the stomach, the large intestines, especially the cecum, have been reported as the most common site for GISTs in dogs.1,2 Metastases can be found in the liver (most common), spleen, mesentery, and mesenteric lymph nodes.2
Gastrointestinal stromal tumor development between the liver and the stomach is rare. In the dog of the present report, the margins of the gastric mass and liver could not be radiographically visualized. Caudodorsal displacement of the gastric axis and leftward displacement of gastric gas usually suggest right-sided hepatomegaly. Although hepatomegaly commonly results in a displacement of the gastric axis, a large gastric neoplasm should be considered when a mass effect cranial to the stomach is observed. When radiographic findings are inconclusive, as in the dog of the present report, ultrasonography can help to determine the location of a mass.
Ultrasonography is a useful technique for evaluating gastrointestinal diseases in small animals. Thickening of the gastric wall along with a loss of wall layering is the most common clinical sign of gastric neoplasia.3 The echogenicity of gastric neoplasm varies dependent on the type of tumor. Gastric leiomyosarcomas and GISTs are often large and have heterogeneous echotextures with mixed echogenic appearances; moreover, some anechoic and hypoechoic regions that represent degeneration and necrosis can also be seen.3,4 Lymphomas and gastric carcinomas are usually hypoechoic and homogeneous.3 Moreover, a gastric wall with a pseudolayering pattern is highly suggestive of gastric carcinoma.5 The size, margins, and echogenicity of GISTs have been classified for predictions of metastatic potential.4 In the dog of the present report, the large size, irregular margins, and heterogeneous echotexture with hyperechoic and hypoechoic regions within the GIST were suggestive of a poor prognosis and high risk of metastasis, consistent with previously reported findings.4 Despite some ultrasonographic features that were suggestive of certain neoplasias, fine-needle aspiration or biopsy is always necessary for cytologic or histopathologic diagnosis and to differentiate tumors from nonneoplastic diseases.
1. Russell KN, Mehler SJ, Skorupski KA, et al. Clinical and immunohistochemical differentiation of gastrointestinal stromal tumors from leiomyosarcomas in dogs: 42 cases (1990–2003).J Am Vet Med Assoc 2007; 230:1329–1333.
2. Frost D, Lasota J, Miettinen M. Gastrointestinal stromal tumors and leiomyomas in the dog: a histopathologic, immunohistochemical, and molecular genetic study of 50 cases. Vet Pathol 2003; 40:42–54.
3. Kaser-Hotz B, Hauser B, Arnold P. Ultrasonographic findings in canine gastric neoplasia in 13 patients. Vet Radiol Ultrasound 1996; 37:51–56.
4. Hanazono K, Fukumoto S, Hirayama K, et al. Predicting metastatic potential of gastrointestinal stromal tumors in dog by ultrasonography. J Vet Med Sci 2012; 74:1477–1482.
5. Penninck DG, Moore AS. Ultrasonography of canine gastric epithelial neoplasia. Vet Radiol Ultrasound 1998; 39:342–348.
