• View in gallery View in gallery View in gallery

    Ventrodorsal (A) and right (B) and left (C) lateral radiographic images of the thorax of an 11-year-old 5.9-kg spayed female American Shorthair with a 4-month history of chronic progressive cough and weight loss and recent onset of tachypnea, dyspnea, regurgitation, anorexia, and right hind limb monoparesis.

  • View in gallery View in gallery View in gallery

    Same images as in Figure 1. A—An alveolar pattern and associated lobar sign are identified in the area of the right middle lung lobe (dashed outline) with adjacent pleural widening. B and C—A rounded, soft tissue opaque structure (arrows) is caudodorsal to the cardiac silhouette, just caudal to the tracheal carina, and the right caudal bronchus is deviated ventrally.

  • View in gallery View in gallery View in gallery

    Postcontrast dorsal (A), sagittal (B), and transverse (C) plane thoracic CT images of the cat described in Figure 1. An amorphous soft tissue–attenuating and heterogeneously contrast-enhancing mass (arrows) surrounds the right main stem bronchus. Secondary to the mass, there is complete attenuation of the bronchi traveling to the right middle, right caudal, and accessory lung lobes (square). At the caudal aspect of the soft tissue structure, there is a structure (star) with a contrast-enhancing rim and composed of material with heterogeneous soft tissue, fluid, and mineral attenuation. The right middle lung lobe (dashed outline) is reduced in volume and diffusely soft tissue opaque with fluid-attenuating material filling the visible airways.

  • 1.

    Wilson DW. Tumors of the respiratory tract. In: Meuten DJ, ed. Tumors in Domestic Animals. John Wiley & Sons; 2016.

  • 2.

    Moulton JE, von Tscharner C, Schneider R. Classification of lung carcinomas in the dog and cat. Vet Pathol. 1981;18(4):513528.

  • 3.

    Hahn KA, McEntee MF. Prognosis factors for survival in cats after removal of a primary lung tumor: 21 cases (1979–1994). Vet Surg. 1998;27(4):307311.

    • Search Google Scholar
    • Export Citation
  • 4.

    Hahn KA, McEntee MF. Primary lung tumors in cats: 86 cases (1979–1994). J Am Vet Med Assoc. 1997;211(10):12571260.

  • 5.

    Ambrosini YM, Johnson KA, Matthews M, Sato AF. Unusual invasion of primary pulmonary adenocarcinoma in a cat. JFMS Open Rep. 2018;4(2):2055116918810897.

    • Search Google Scholar
    • Export Citation
  • 6.

    Aarsvold S, Reetz JA, Reichle JK, et al. Computed tomographic findings in 57 cats with primary pulmonary neoplasia. Vet Radiol Ultrasound. 2015;56(3):272277.

    • Search Google Scholar
    • Export Citation
  • 7.

    Prather AB, Berry CR, Thrall DE. Use of radiography in combination with computed tomography for the assessment of noncardiac thoracic disease in the dog and cat. Vet Radiol Ultrasound. 2005;46(2):114121.

    • Search Google Scholar
    • Export Citation

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  • 1 Department of Small Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M, College Station, TX
  • | 2 Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M, College Station, TX

Abstract

In collaboration with the American College of Veterinary Radiology

Abstract

In collaboration with the American College of Veterinary Radiology

History

An 11-year-old 5.9-kg spayed female American Shorthair was referred to the Texas A&M University Veterinary Medical Teaching Hospital because of a 4-month history of a chronic progressive cough and weight loss and recent onset of tachypnea, dyspnea, regurgitation, anorexia, and right hind limb monoparesis. The cat had a 4-month history of a cough, which had progressed to intermittent hemoptysis. This was treated empirically with intermittent cefovecin injections, with no improvement, and by 1 month prior to presentation, the patient had been observed to sneeze blood as well. The respiratory signs were accompanied by progressive inappetence, and by presentation, the cat had been anorexic for almost 5 days. In tandem with a decrease in appetite, the owner reported that the cat had begun to appear dysphagic, with difficulty swallowing and regurgitation of recently consumed treats. The cat’s sudden increase in respiratory rate and effort occurred the morning of presentation and was not precipitated by a particular event. Also, on that morning, the cat was seen intermittently dragging her right hind limb and had been noticeably ataxic in both hind limbs the night prior.

On presentation, the cat was alert but tachypneic with a respiratory rate of approximately 90 breaths/min and a mild increase in respiratory effort. On auscultation, muffled bronchovesicular sounds were heard over the right hemithorax. The patient was also estimated to be dehydrated at approximately 5% to 7% body weight fluid deficit. No hind limb lameness nor ataxia was appreciated. The patient was obese with a body condition score of 8/9. Peripheral blood glucose concentrations were measured in the right forelimb, left hind limb, and right hind limb, and results (glucose concentration range, 96 to 116 mg/dL) were not consistent with arterial thromboembolism. Femoral pulses were palpated bilaterally. An initial CBC identified a stress leukogram and moderate thrombocytopenia (74 X 103 platelets/µL; reference range, 151 X 103 to 600 X 103 platelets/µL), but this had improved by the following morning (114 X 103 platelets/µL) and platelet clumping was noted. Biochemical analyses revealed mildly high alanine aminotransferase activities (162 U/L, reference range, 12 to 130 U/L). A point-of-care N-terminal pro-B-type natriuretic peptide ELISA (SNAP Feline proBNP Test, Idexx Laboratories Inc) was performed to screen for underlying cardiac disease, and the result was positive. Total thyroxine concentration was clinically normal (1.19 µg/dL; reference range, 0.78 to 3.82 µg/dL). The patient received butorphanol (0.2 mg/kg, IV) and supplemental oxygen for stabilization, and 3-view (right lateral, left lateral, and ventrodorsal views) thoracic radiography was performed (Figure 1).

Figure 1
Figure 1
Figure 1
Figure 1

Ventrodorsal (A) and right (B) and left (C) lateral radiographic images of the thorax of an 11-year-old 5.9-kg spayed female American Shorthair with a 4-month history of chronic progressive cough and weight loss and recent onset of tachypnea, dyspnea, regurgitation, anorexia, and right hind limb monoparesis.

Citation: Journal of the American Veterinary Medical Association 259, S1; 10.2460/javma.21.01.0041

Formulate differential diagnoses, then continue reading.

Diagnostic Imaging Findings and Interpretation

An alveolar pulmonary pattern at the level of the right middle lung lobe and mild widening of the adjacent pleural space were identified. On the ventrodorsal projection, the caudal mediastinum was widened, and on the lateral projections, directly caudal and dorsal to the carina at the caudodorsal margin of the heart, an ill-defined soft tissue opaque structure was identified (Figure 2). There was ventral deviation of the right caudal bronchus on the left lateral view with irregular curvature of the caudal vena cava, which was not seen on the right lateral view. No tracheal deviation was noted. The remaining lung fields and pleural space were normal. Given these findings, the top differential diagnosis was bronchopneumonia affecting the right middle lung lobe with adjacent minimal pleural effusion. Due to the structure identified at the caudodorsal margin of the cardiac silhouette, as well as the patient’s dysphagia and regurgitation, there was concern for either an esophageal foreign body, tracheobronchial lymphadenopathy, or mediastinal mass resulting in obstruction, regurgitation, and secondary aspiration pneumonia. Mild cardiomegaly was noted, with the cardiac silhouette spanning 3.5 intercostal spaces in width on the right lateral view. The caudal vena cava, pulmonary vasculature, and aorta were considered unremarkable. To further assess the structures in the thorax, CT was pursued.

Figure 2
Figure 2
Figure 2
Figure 2

Same images as in Figure 1. A—An alveolar pattern and associated lobar sign are identified in the area of the right middle lung lobe (dashed outline) with adjacent pleural widening. B and C—A rounded, soft tissue opaque structure (arrows) is caudodorsal to the cardiac silhouette, just caudal to the tracheal carina, and the right caudal bronchus is deviated ventrally.

Citation: Journal of the American Veterinary Medical Association 259, S1; 10.2460/javma.21.01.0041

The patient underwent general anesthesia for contrast CT of the head and thorax (Figure 3). Surrounding the right main stem bronchus, just caudal to the bifurcation, a large focus of amorphous soft tissue–attenuating and heterogeneously contrast-enhancing material was identified, with associated complete attenuation of the bronchi to the right middle, right caudal, and accessory lung lobes. The right caudal lung lobe, right middle lung lobe, and the accessory lung lobe were reduced in volume with patchy ground-glass attenuation and with soft tissue– and fluid-attenuating material filling the visible airways. There was a small volume of pleural effusion noted. The top differential diagnosis was a neoplastic pulmonary mass, particularly an adenocarcinoma, resulting in partial to complete secondary atelectasis of the right middle, right caudal, and accessory lung lobes.

Figure 3
Figure 3
Figure 3
Figure 3

Postcontrast dorsal (A), sagittal (B), and transverse (C) plane thoracic CT images of the cat described in Figure 1. An amorphous soft tissue–attenuating and heterogeneously contrast-enhancing mass (arrows) surrounds the right main stem bronchus. Secondary to the mass, there is complete attenuation of the bronchi traveling to the right middle, right caudal, and accessory lung lobes (square). At the caudal aspect of the soft tissue structure, there is a structure (star) with a contrast-enhancing rim and composed of material with heterogeneous soft tissue, fluid, and mineral attenuation. The right middle lung lobe (dashed outline) is reduced in volume and diffusely soft tissue opaque with fluid-attenuating material filling the visible airways.

Citation: Journal of the American Veterinary Medical Association 259, S1; 10.2460/javma.21.01.0041

Just caudal to the tracheal bifurcation and contiguous with the previously described amorphous soft tissue–attenuating mass in the right lung, a rounded structure was identified at midline. This structure was encapsulated by a soft tissue–attenuating and contrast-enhancing rim and was composed of fluid- and mineral-attenuating material and was suspected to be a necrotic or cystic portion of the primary lung tumor with concurrent dystrophic mineralization, with less likely differential diagnosis being a necrotic metastatic tracheobronchial lymph node. This structure displaced the esophagus dorsally and to the left, resulting in a focal compression against the aorta. There was also mild focal rightward deviation of the caudal vena cava. The intrathoracic portion of the esophagus otherwise contained a small volume of gas. There was also (not shown) a lobular soft tissue–attenuating nodule within the caudal aspect of the right cranial lung lobe that was presumed to be a metastatic nodule.

Treatment and Outcome

Tracheobronchoscopy was recommended to further visualize the mass and to acquire tissue samples for histopathology but was declined. Potential treatment options included radiation therapy or surgical intervention but given the progressive clinical signs and location of the mass, the owners elected euthanasia for the cat.

On necropsy, a mass was identified extending from the right middle lung lobe to the tracheal carina and was histologically diagnosed as pulmonary adenocarcinoma with basosquamous differentiation. Associated with this mass was a cavitated region filled with yellow to gray, gelatinous to caseous material, consistent with necrosis. The bronchi associated with the mass were expanded and congested by mucous, most severely noted in the right caudal lobe, distal to the mass. There was also evidence of metastasis of this tumor to the kidneys. Histology of the nodule within the right cranial lung lobe—while also consistent with pulmonary adenocarcinoma—had a lepidic component, and so this nodule was believed to have been a separate primary tumor rather than metastasis. Necropsy also identified evidence of disseminated small-cell lymphoma within the lungs, liver, and colon. The clinical importance of this finding was unknown.

Comments

The cat of the present report had pulmonary adenocarcinoma. Pulmonary neoplasms are uncommon in cats and are thought to represent < 1% of feline cancers.1 Among these, pulmonary adenocarcinomas are most common, followed by alveolar and squamous cell carcinomas.2 Most often, pulmonary adenocarcinomas affect the caudal lung lobes, and cats typically present with signs related to the respiratory tract, such as coughing, wheezing, and tachypnea. In some cases, however, signs are less specific and can include weight loss, lameness, and lethargy.3,4 In the cat of the present report, pulmonary adenocarcinoma not only resulted in weight loss and respiratory compromise but also regurgitation. Regurgitation has been previously reported5 in a cat with a pulmonary adenocarcinoma located in a similar location, but in that instance, the tumor had invaded the esophagus resulting in a focal stricture, whereas in our patient the esophagus was suspected to have been compressed against the aorta. Pulmonary adenocarcinomas behave aggressively in cats, with metastasis identified in 53% (pulmonary) to 75% (all sites) of cats. Though less common, extrathoracic metastasis to abdominal organs such as the liver and kidney has been documented.4,6 Due to the high rate of metastasis, long-term prognosis, regardless of treatment, is guarded. In a group of 21 cats that underwent surgical removal of the affected lung lobe or lobes, the median survival time was 115 days.3

This case exemplifies the challenges and limitations associated with radiographs when investigating intrathoracic disease. Although the alveolar pattern identified on radiographs was most consistent with bronchopneumonia, CT provided clear evidence of a mass and showed that the consolidated lung represented atelectasis secondary to airway occlusion. The difference in the interpretation of these 2 diagnostics demonstrates the role of thoracic radiographs as a screening tool and the utility of advanced imaging in more complex cases. In a group of dogs and cats with noncardiac disease that underwent thoracic radiographs and CT, the CT provided additional case information in the vast majority of dogs (75%) and in all cats.7 CT has proven to be superior to radiographs when investigating intrathoracic pathology, being capable of producing images with exceptional detail while being less affected by superimposition of soft tissue structures. Due to this, multiple studies report the use of thoracic CT for assessing feline pulmonary neoplasia, and as seen in the reported case, this imaging modality allows for more precise measures of tumor growth such as bronchial compression and invasion to be identified.6

Acknowledgments

No third-party funding or support was received in connection with this case or the writing or publication of the manuscript. The authors declare that there were no conflicts of interest.

References

  • 1.

    Wilson DW. Tumors of the respiratory tract. In: Meuten DJ, ed. Tumors in Domestic Animals. John Wiley & Sons; 2016.

  • 2.

    Moulton JE, von Tscharner C, Schneider R. Classification of lung carcinomas in the dog and cat. Vet Pathol. 1981;18(4):513528.

  • 3.

    Hahn KA, McEntee MF. Prognosis factors for survival in cats after removal of a primary lung tumor: 21 cases (1979–1994). Vet Surg. 1998;27(4):307311.

    • Search Google Scholar
    • Export Citation
  • 4.

    Hahn KA, McEntee MF. Primary lung tumors in cats: 86 cases (1979–1994). J Am Vet Med Assoc. 1997;211(10):12571260.

  • 5.

    Ambrosini YM, Johnson KA, Matthews M, Sato AF. Unusual invasion of primary pulmonary adenocarcinoma in a cat. JFMS Open Rep. 2018;4(2):2055116918810897.

    • Search Google Scholar
    • Export Citation
  • 6.

    Aarsvold S, Reetz JA, Reichle JK, et al. Computed tomographic findings in 57 cats with primary pulmonary neoplasia. Vet Radiol Ultrasound. 2015;56(3):272277.

    • Search Google Scholar
    • Export Citation
  • 7.

    Prather AB, Berry CR, Thrall DE. Use of radiography in combination with computed tomography for the assessment of noncardiac thoracic disease in the dog and cat. Vet Radiol Ultrasound. 2005;46(2):114121.

    • Search Google Scholar
    • Export Citation

Contributor Notes

Corresponding author: Dr. Evans (Jbevans12@tamu.edu)