History
A 7-year-old spayed female domestic shorthair cat with a history of nasal lymphoma was evaluated for acute respiratory distress. Approximately 2 years prior, a mass was resected from the nasal cavity and histologic findings were consistent with lymphoma. Results of tumor staging, including thoracic radiography, were negative for lymphoma elsewhere. The cat was treated with chemotherapy for 2 years, and there was no evidence of local or distant recurrence of lymphoma during that time. Physical examination revealed no clinical abnormalities other than respiratory distress that was localized to the upper airway. The cat was managed with oxygen therapy (O2 cage) and mild sedation. A CBC and serum biochemical analysis were performed once the cat was stabilized, and no abnormalities were identified. Thoracic radiographs from the referring veterinarian were available for interpretation (Figure 1).
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Diagnostic Imaging Findings and Interpretation
The tracheal lumen is decreased in diameter at the level of C5-C7, and the tracheal wall is obscured by a poorly defined soft tissue opacity superimposed with the lumen (Figure 2). On the basis of the radiographic findings, tracheal stenosis was suspected. Differential diagnoses included tracheal neoplasia, tracheal stricture, granuloma, and tracheal foreign body.
A computed tomographic scan of the head, trachea, and thorax was performed under general anesthesia with a slice thickness of 2.5 mm and standard algorithm. Tracheal wall thickening from the level of C5-C6, causing partial tracheal stenosis, was identified. At the level of C6, the mural infiltration appeared to extend into the peritracheal region at the dorsal and right lateral aspects of the trachea with uniform contrast enhancement (Figure 3). No evidence of disease in the nasal cavity, brain, and thorax was observed.
Comments
Fine-needle aspiration of the tracheal mass was performed under ultrasound guidance by use of a ventral approach, and a cytologic diagnosis of lymphoma was made. Abdominal ultrasonography was performed to further stage the recurrent lymphoma and revealed no abnormalities.
Primary tumors of the trachea are uncommon in dogs and cats. Usually, dogs and cats with primary tracheal neoplasia are middle-aged or older; however, young animals with active osteochondral ossification sites are at risk for benign tracheal osteochondromas.1,2 Primary tracheal neoplasms of dogs and cats include lymphoma, plasma cell tumors, chondrosarcoma, adenocarcinomas, and squamous cell carcinoma; lymphoma and thyroid adenocarcinoma have been reported to invade the trachea.2
Dogs and cats with tracheal neoplasia usually have a history of coughing, dyspnea, wheezing, stridor, or change in voice or bark.1,2 Because small animals with respiratory distress are often clinically unstable, procedures to further evaluate these patients such as radiography, ultrasonography, cross-sectional imaging, and tissue specimen collection must be performed under sedation or anesthesia and with great care to avoid further trauma to the respiratory tract. Survey radiography, ultrasonography, computed tomography, and magnetic resonance imaging of the cervical region and thorax may help to further determine the extent of the mass and guide biopsy procedures in a minimally invasive manner. Further diagnostic tools may include endoscopic biopsy of the tracheal mass and assessment of the lumen.1,3
Treatment options for tracheal tumors include surgical excision and anastomosis, chemotherapy, radiation therapy, or a combination of these treatment modalities. Lymphoma is considered to be sensitive to radiation therapy,4 and response to radiation is often rapid. Combination chemotherapy is the current minimal recommended treatment.1
Because there was no evidence of lymphoma elsewhere in the cat of this report, radiation therapy was administered. The cat's respiratory distress resolved after 2 fractions of radiation, and the cat completed a 10-fraction course of treatment (total dose of 36 Gy administered by a linear accelerator). After the last fraction of radiation, an ultrasonographic examination of the trachea was repeated, revealing a reduction in size of the tracheal mass. Thoracic radiographs were made 7 days after treatment and revealed a distinct decrease in the size of the mass such that the stenosis was no longer evident.
Chemotherapy with lomustine was initiated because the tumor represented a recurrence of lymphoma in this cat. The cat did well clinically until it was brought to the referring veterinarian with acute onset of neurologic signs (dementia, circling, and absent menace reflex) 15 days after the last radiation treatment. The owner elected euthanasia without pursuing further diagnostic testing. Necropsy did not reveal any histologic abnormalities in the brain; however, neoplastic lymphocytes were found in the kidneys, heart, adrenal gland, and dorsal ligament of the trachea.
- 1.↑
Brown MR, Rogers KS & Mansell KJ, et al. Primary intratracheal lymphosarcoma in four cats. J Am Anim Hosp Assoc 2003;39:468–472.
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Rachel MB, Rogers KS. Primary tracheal tumors in dogs and cats. Compend Contin Educ Pract Vet 2003;25:854–860.
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Withrow SJ. Tumors of the trachea. In: Withrow SJ, Vail DM, eds. Withrow and MacEwen's small animal clinical oncology. 4th ed. St Louis: Saunders Elsevier Inc, 2007;515–516.
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Fertil B, Malaise EP. Intrinsic radiosensitivity of human cell lines is correlated with radioresponsiveness of human tumors: analysis of 101 published survival curves. Int J Radiat Oncol Biol Phys 1985;11:1699–1707.