Pulmonary carcinoma

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Mixed-pattern primary pulmonary adenocarcinoma[1]

Primary pulmonary carcinoma are a relatively rare neoplasia of dogs characterized by primary lung disease[2].

Primary lung tumors are rare in dogs (majority a result of inhaled carcinogens[3]), whereas pulmonary metastatic neoplastic involvement is common[4], usually mammary adenocarcinoma and anal sac adenocarcinoma[5]. Unlike secondary metastatic neoplasms, primary pulmonary carcinomas rarely produce hypertrophic osteoarthropathy.

Pulmonary adenocarcinoma is the most common primary lung neoplasia in dogs, with secondary metastasis to regional lymph nodes and the heart common. Alveolar carcinoma and squamous cell carcinoma also occur and anaplastic large-cell carcinomas are considered rare[6].

These tumors are usually classified as either differentiated or undifferentiated based on histologic pattern rather than histogenesis[7]. As metastatic rate and survival appear to vary with classification, pattern distinction is of primary prognostic importance[8].

Affected dogs usually present with coughing, dyspnea, inspiratory wheezing, epistaxis, fever, weight loss and anorexia. Pulmonary edema and hypertrophic osteoarthropathy have been reported in advanced cases[9].

Diagnosis is based on imaging with radiography, CT or MRI. Transcutaneous pulmonary biopsy, tracheobronchial washes or tracheal endoscopy are frequently employed to assist diagnosis.

Radiographically, these tumor may appear as a single mass or a nodular-disseminated growth, mimicking the metastatic involvement of the lung.

A definitive diagnosis usually requires histopathology of biopsied material.

Immunohistochemistry of biopsies usually shows negative staining for vimentin with papillary adenocarcinomas while adenocarcinomas usually stain positive for cytokeratin[1].

Regional mediastinal lymphadenopathy is suggestive of a poorer prognosis.

A differential diagnosis would include heartworm disease, lymphoma, cranial mediastinal carcinoma[10], lungworm (e.g. Filaroides osleri), bronchial carcinoma, metastatic mammary adenocarcinoma, Coccidioides spp, Aspergillus spp, Nocardia spp and Mycobacterium spp[11].

Treatment usually requires lobectomy via thoracotomy or endoscopy in cases where the trachea is unaffected by metastases[12], and is usually curative[13]. Adjunct radiation therapy or chemotherapy may be required.

Systemic chemotherapy, intrapleural chemotherapy or both with combinations of cisplatin, carboplatin and mitoxantrone have been employed for treating malignant pleural effusions.

Long term remission is good for small differentiated adenocarcinomas. Undifferentiated carcinomas have over a 50% incidence of metastasis. The prognosis for squamous cell carcinoma is poor with a metastasis rate of over 90%.

References

  1. 1.0 1.1 Burgess HJ & Kerr ME (2009) Cytokeratin and vimentin co-expression in 21 canine primary pulmonary epithelial neoplasms. J Vet Diagn Invest 21(6):815-820
  2. Hahn FF et al (1996) Primary lung neoplasia in a beagle colony. Vet Pathol 33(6):633-638
  3. Bettini G et al (2010) Association between environmental dust exposure and lung cancer in dogs. Vet J 186(3):364-369
  4. Conti MB et al (2010) A case of primary papillary disseminated adenocarcinoma of canine lung. Vet Res Commun 34(1):S111-S115
  5. Hammond TN et al (2009) What is your diagnosis? Metastatic anal sac adenocarcinoma with paraneoplastic hypertrophic osteopathy. J Am Vet Med Assoc 235(3):267-268
  6. Ogilvie GK et al (1989) Classification of primary lung tumors in dogs: 210 cases (1975–1985). J Am Vet Med Assoc 195:106–108
  7. Dungworth DL et al (1999) Histologic classification of tumors of the respiratory system of domestic animals, 2nd ed. Armed Forces Institute of Pathology, Washington, DC
  8. Polton GA et al (2008) Impact of primary tumour stage on survival in dogs with solitary lung tumours. J Small Anim Pract 49:66–71
  9. Ramoo S (2013) Hypertrophic osteopathy associated with two pulmonary tumours and myocardial metastases in a dog: a case report. N Z Vet J 61(1):45-48
  10. Liptak JM et al (2008) Cranial mediastinal carcinomas in nine dogs. Vet Comp Oncol 6(1):19-30
  11. Jones BG & Pollard RE (2012) Relationship between radiographic evidence of tracheobronchial lymph node enlargement and definitive or presumptive diagnosis. Vet Radiol Ultrasound 53(5):486-491
  12. Laksito MA et al (2010) Thoracoscopic-assisted lung lobectomy in the dog: report of two cases. Aust Vet J 88(7):263-267
  13. Mosing M et al (2008) Endoscopic removal of a bronchial carcinoma in a dog using one-lung ventilation. Vet Surg 37(3):222-225
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