History
An 8-year-old 9.5-kg (21-lb) spayed female miniature Schnauzer was referred for evaluation of acute dyspnea of 1 day's duration. Three months prior to referral, the dog had anaplastic sarcoma that had been surgically resected from the subcutis of the right antebrachium with incomplete margins. On initial examination, the dog was in respiratory distress with a respiratory rate of 72 breaths/min, a heart rate of 160 beats/min, and marked inspiratory effort. The patient was immediately moved to the oxygen cage, which resulted in minimal clinical improvement. Thoracic auscultation revealed decreased lung sounds in the right lung field. Marked stridor was noted on auscultation of the thoracic inlet. The remainder of the physical examination was unremarkable.
Hematologic abnormalities included mild neutrophilia (12,170 neutrophils/μL; reference range, 3,000 to 12,000 neutrophils/μL); no other abnormalities were noted on CBC. Abnormalities detected on serum biochemical analysis included elevation in serum alkaline phosphatase (840 U/L; reference range, 20 to 160 U/L) and alanine transferase (312 U/L; reference range, 10 to 118 U/L) activities and mild elevation in blood glucose (117 mg/dL; reference range, 60 to 110 mg/dL) concentration. Thoracic radiographs were obtained (Figure 1).
Right lateral (A) and dorsoventral (B) radiographic views of the thorax of an 8-year-old 9.5-kg (21-lb) spayed female miniature Schnauzer with a 1-day history of acute respiratory distress.
Citation: Journal of the American Veterinary Medical Association 248, 5; 10.2460/javma.248.5.489
Right lateral (A) and dorsoventral (B) radiographic views of the thorax of an 8-year-old 9.5-kg (21-lb) spayed female miniature Schnauzer with a 1-day history of acute respiratory distress.
Citation: Journal of the American Veterinary Medical Association 248, 5; 10.2460/javma.248.5.489
Right lateral (A) and dorsoventral (B) radiographic views of the thorax of an 8-year-old 9.5-kg (21-lb) spayed female miniature Schnauzer with a 1-day history of acute respiratory distress.
Citation: Journal of the American Veterinary Medical Association 248, 5; 10.2460/javma.248.5.489
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
A mediastinal shift to the right is evident with rightward deviation of the trachea and the cardiac silhouette in the dorsoventral image. An increase in soft tissue opacity is visible within the dorsal portion of the right cranial, middle, caudal, and accessory lung lobes on the lateral and ventrodorsal images, causing border effacement of the right and caudal aspect of the cardiac silhouette as well as the caudal vena cava (Figure 2). An ovoid, partially well-defined, smoothly marginated, soft tissue opaque nodule measuring 1.5 cm in diameter is visible within the tracheal bifurcation occluding the lumen of the right caudal mainstem bronchus, which is best seen on the right lateral view. On the basis of radiographic findings, airway occlusion of the right mainstem bronchus with associated atelectasis or noncardiogenic pulmonary edema was diagnosed. Differential diagnoses for the intratracheal soft tissue nodule included tracheal foreign body, extension of pulmonary neoplasia, tracheal neoplasia, and granuloma.
Same radiographic images as in Figure 1. A—Notice the well-defined soft tissue opaque nodule within the tracheal lumen at the bifurcation (arrows). An ill-defined soft tissue opacity is evident within the caudodorsal aspect of the thorax, causing border effacement of the cardiac silhouette and the caudal vena cava. B—Increased soft tissue opacity of all right lung lobes is evident, with mediastinal shift of the cardiac silhouette to the right (asterisk) indicating atelectasis on the right side. Border effacement of the right side of the heart is present. The left mainstem bronchus is observable (arrows); the right mainstem bronchus cannot be identified. There is mild asymmetry of the right 8th to 10th ribs caused by rotation of the dog.
Citation: Journal of the American Veterinary Medical Association 248, 5; 10.2460/javma.248.5.489
Same radiographic images as in Figure 1. A—Notice the well-defined soft tissue opaque nodule within the tracheal lumen at the bifurcation (arrows). An ill-defined soft tissue opacity is evident within the caudodorsal aspect of the thorax, causing border effacement of the cardiac silhouette and the caudal vena cava. B—Increased soft tissue opacity of all right lung lobes is evident, with mediastinal shift of the cardiac silhouette to the right (asterisk) indicating atelectasis on the right side. Border effacement of the right side of the heart is present. The left mainstem bronchus is observable (arrows); the right mainstem bronchus cannot be identified. There is mild asymmetry of the right 8th to 10th ribs caused by rotation of the dog.
Citation: Journal of the American Veterinary Medical Association 248, 5; 10.2460/javma.248.5.489
Same radiographic images as in Figure 1. A—Notice the well-defined soft tissue opaque nodule within the tracheal lumen at the bifurcation (arrows). An ill-defined soft tissue opacity is evident within the caudodorsal aspect of the thorax, causing border effacement of the cardiac silhouette and the caudal vena cava. B—Increased soft tissue opacity of all right lung lobes is evident, with mediastinal shift of the cardiac silhouette to the right (asterisk) indicating atelectasis on the right side. Border effacement of the right side of the heart is present. The left mainstem bronchus is observable (arrows); the right mainstem bronchus cannot be identified. There is mild asymmetry of the right 8th to 10th ribs caused by rotation of the dog.
Citation: Journal of the American Veterinary Medical Association 248, 5; 10.2460/javma.248.5.489
Bronchoscopy was performed following radiography with the goal of removing a portion of the obstruction. A large, well-vascularized, firm mass was found in the right mainstem bronchus that occluded 90% of the airway. The mass was removed with an endoscopic-guided rigid forceps; a small portion of the stem remained. Cytologic and histologic evaluation of the mass revealed round to spindle-shaped cells that occurred singly and in large clusters. These cells had marked anisokaryosis (occasionally with giant single nucleus), stippled chromatin, and prominent nucleoli that varied in number and size. Several binucleated and some multinucleated forms were present. These findings were consistent with a sarcoma.
After bronchoscopy, thoracic radiographs were obtained. A soft tissue nodule within the caudal portion of the trachea was evident as well as persistent soft tissue opacity within the right cranial, middle, and accessory lung lobes, with increased aeration in the right caudal lung lobe, compared with previous radiographic images (Figure 3). Differential diagnoses for the persistent radiographic changes of the right lung lobes included pulmonary neoplasia, atelectasis, hemorrhage, pneumonia, and acute respiratory distress syndrome.
Right lateral (A) and ventrodorsal (B) radiographic views of the dog in Figure 1 obtained immediately after bronchoscopy and tracheal mass excision. An endotracheal tube is in place within the trachea. Compared with radiographs obtained before bronchoscopy, the mediastinal shift is reduced with the cardiac silhouette at midline. The increased soft tissue opacity within the right lung lobes continues to obscure the caudal cardiac border and caudal vena cava. The bronchus of the right caudal lung lobe is still not identified.
Citation: Journal of the American Veterinary Medical Association 248, 5; 10.2460/javma.248.5.489
Right lateral (A) and ventrodorsal (B) radiographic views of the dog in Figure 1 obtained immediately after bronchoscopy and tracheal mass excision. An endotracheal tube is in place within the trachea. Compared with radiographs obtained before bronchoscopy, the mediastinal shift is reduced with the cardiac silhouette at midline. The increased soft tissue opacity within the right lung lobes continues to obscure the caudal cardiac border and caudal vena cava. The bronchus of the right caudal lung lobe is still not identified.
Citation: Journal of the American Veterinary Medical Association 248, 5; 10.2460/javma.248.5.489
Right lateral (A) and ventrodorsal (B) radiographic views of the dog in Figure 1 obtained immediately after bronchoscopy and tracheal mass excision. An endotracheal tube is in place within the trachea. Compared with radiographs obtained before bronchoscopy, the mediastinal shift is reduced with the cardiac silhouette at midline. The increased soft tissue opacity within the right lung lobes continues to obscure the caudal cardiac border and caudal vena cava. The bronchus of the right caudal lung lobe is still not identified.
Citation: Journal of the American Veterinary Medical Association 248, 5; 10.2460/javma.248.5.489
Treatment and Outcome
The patient recovered uneventfully from anesthesia. No abnormalities were detected on arterial blood gas analysis. Overnight, the dog received sedation and antimicrobials for supportive care. The next day, the dog began to exhibit signs of labored breathing and increased respiratory rate. Thoracic radiographs were obtained, and a recurrent well-defined soft tissue nodule was seen in the caudal portion of the trachea as well as evidence of ventral patchy alveolar disease in the left cranial lung lobe. Similar changes were observed in the right lung lobes. Differential diagnoses for the left cranial lung lobe alteration included aspiration pneumonia, hemorrhage from previous mass excision, or acute respiratory distress syndrome. Differential diagnoses for the recurrent mass included recurrence of the sarcoma from either extension from the pulmonary parenchyma or trachea, or a hematoma from excision of the previous mass. Because of the poor prognosis, the owner elected to have the dog euthanized and necropsy was declined.
Comments
Primary tumors affecting the airways are uncommon in dogs and cats.1 Most tumors appear radiographically as solitary intraluminal masses; however, tracheal tumors in cats can appear as diffuse thickening of the lumen as seen with lymphoma.2 The tumors are primarily located in the trachea and are less likely to occur in the mainstem bronchus or at the carina.2 Nonetheless, occlusion of a mainstem bronchus may also occur from primary tumors of the trachea, or they may occur from invading metastatic or invading primary lung tumors.2 The most common type of tracheal tumor in dogs is reportedly osteochondroma, occurring more commonly in young dogs, typically < 2 years of age.2 Other primary tracheal tumors of dogs and cats include neuroendocrine tumor, lymphoma, plasma cell tumor, chondrosarcoma, adenocarcinoma, and squamous cell carcinoma.2–6 Clinical signs observed in dogs and cats with tracheal tumors include dyspnea, cough, exercise intolerance, cyanosis, inability to bark, physical collapse, or weight loss; however, if the tumor is associated with the larynx, stridor and voice change may be observed.4 Tumor type is primarily determined on the basis of cytologic and histologic findings on evaluation of biopsy specimens.4 Treatment of tracheal tumors is primarily dictated by tumor type and stage.4 Tracheal resection and anastomosis have been reported; radiation therapy and chemotherapy have also been useful in treating these tumors.1 On the basis of the occlusion of the mainstem bronchus and clinical signs of the dog in the present report, removal of the tumor was performed to improve overall respiratory signs, stabilize the patient, and obtain a definitive diagnosis. Euthanasia was elected after the patient deteriorated overnight following tumor removal. The final histopathologic diagnosis was an anaplastic sarcoma cytomorphologically similar to the tumor previously excised from the antebrachium. It is possible that this was a metastatic lesion extending from the lung parenchyma or may have been strictly associated with the wall of the trachea. Although recurrence of a neoplastic mass a day after removal may appear unlikely, this remains a possibility considering the markedly anaplastic nature of the neoplastic cells in the dog of the present report.
References
1. Withrow SJ, Vail DM, Page R. Withrow and MacEwen's small animal clinical oncology. St Louis: Elsevier Health Sciences, 2013;451–452.
2. Carlisle C, Biery DN, Thrall DE. Tracheal and laryngeal tumors in the dog and cat: literature review and 13 additional patients. Vet Radiol 1991; 32: 229–235.
3. Gould EN, Johnson LR, Traslavina RP, et al. Neuroendocrine tumour at the carina of a dog. J Comp Pathol 2013; 149: 233–236.
4. Brown MR, Rogers KS. Primary tracheal tumors in dogs and cats. Compend Contin Educ Pract Vet 2003; 25: 854–860.
5. Hayes AM, Gregory SP, Murphy S, et al. Solitary extramedullary plasmacytoma of the canine larynx. J Small Anim Pract 2007; 48: 288–291.
6. Bell R, Philbey AW, Martineau H, et al. Dynamic tracheal collapse associated with disseminated histiocytic sarcoma in a cat. J Small Anim Pract 2006; 47: 461–464.
