History and Presenting Complaint:

“Christy” was a 16.5 year old, female spayed canine mix breed weighing 21.6 kg.
She presented to VESCONE for 1-2 days of a dry cough that was worse at night. She had become progressively weaker and lethargic with a decreasing appetite over the last 4 days. Previous medical history was limited to weight loss over the last 6 months and arthritis for which she received 12.5 mg Vioxx as needed.

Physical Exam:

“Christy” was emaciated with complete muscle wasting. She walked with effort and maintained a hunched stance. She was tachycardic with a resting heart rate of 140 beats per minute and had a 2/6 holosystolic murmur. She had a fever of 103.4 F and several soft subcutaneous masses. All other systems were within normal limits.

Diagnostics and Therapeutics:

Blood work and thoracic radiographs were performed. A complete blood count, biochemical profile, and coagulation panel were unremarkable.
Thoracic films revealed a 6 cm soft tissue opacity in the right medial lung lobe, dorsal to the heart, as well as spondylosis. Differential diagnoses for the soft tissue opacity included neoplasia, infection, granuloma/inflammation, and cyst.
The following day, ultrasound of the thoracic cavity and ultrasound guided fine needle aspirate of the soft tissue opacity were performed. The ultrasound showed a 6 cm mass with few cavitations in the right middle lung lobe. The primary rule out was a primary or secondary pulmonary mass. Cytological interpretation of the fine needle aspirate revealed a malignant epithelial tumor, most likely a pulmonary carcinoma, with necrotic debris and secondary inflammation.
“Christy” was hospitalized for 48 hours. She was placed on intravenous fluids. Initially, her temperature normalized on IV fluids. When her fever recurred after 24 hours on fluids, she was given an injection of Ketofen and sent home on 375 mg Clavamox twice daily. Follow up with an oncologist was recommended.

Follow Up:

Five days after her presentation to VESCONE, “Christy” presented to the New England Veterinary Oncology Group for a follow up consultation. Physical exam findings were similar to her examination at VESCONE, however swelling over multiple joints with the left carpus and tarsus most severely affected, was also noted. Radiographs of the tarsus and carpus revealed periosteal proliferation and carpal and tarsal joint swelling. A radiographic diagnosis of Hypertrophic Osteopathy was made.
After discussing treatment options, including surgical removal of the pulmonary tumor and further diagnostics to rule out the presence of other masses, “Christy’s” owner elected palliative treatment. Clavamox was discontinued, and “Christy” was sent home with Hycodan as needed for cough and 0.5 mg/kg Prednisone twice daily with a recommendation to recheck thoracic radiographs in 4-6 weeks.

Discussion:

The most common causes of primary pulmonary neoplasia in the dog and cat are adenocarcinomas (70-80%) followed by squamous cell and anaplastic carcinomas. Less common are fibrosarcoma, osteosarcoma, chondrosarcoma and hemangiosarcoma. Benign adenomas are infrequent findings. It is more common to find metastatic tumors in the chest, which can be caused by any malignant tumor. The most common causes of pulmonary metastases include thyroid and mammary carcinomas, osteosarcoma and hemangiosarcoma, transitional cell carcinoma, oral and digital melanoma and squamous cell carcinoma.
Treatment for primary pulmonary neoplasia is excision of the tumor, which usually requires a lung lobectomy. Chemotherapy can be attempted in cases where surgical removal is not recommended, however it is not considered to be very effective. Prognosis is guarded especially if metastasis or other disease is present. In dogs with no signs of metastasis where all macroscopic disease has been removed, survival time of 20 months or greater has been reported. In cases of metastatic pulmonary tumors, the presence of other disease caused by the tumor and type of tumor may determine whether surgical removal of the lung mass is indicated.
Hypertrophic osteoarthropathy or hypertrophic pulmonary osteopathy (HO) is a disorder of the bony extremities that usually occurs secondary to intrathoracic disease. It is uncommon in dogs and rare in cats. Dogs suffering from HO present with painful swelling of the distal limbs. Diagnosis is made from the characteristic radiographic appearance. Commonly, these dogs have concurrent intrathoracic disease including primary or metastatic pulmonary or esophageal tumors, heartworm, pneumonitis or endocarditis. HO has also been associated, although rarely, with liver, bladder and ovarian tumors. The pathogenesis of HO is not fully understood. It appears to be a vagally mediated increase of blood flow to the distal extremities causing an overgrowth of connective tissue. Although HO occurs secondary to an underlying disease, many pets will present for signs of HO rather than thoracic disease. Full regression of HO occurs over a period of weeks to months if the underlying disease is corrected. Glucocorticoids and non-steroidal anti-inflammatories may improve clinical signs and patient comfort. Vagotomy has also been suggested as a treatment option.
In “Christy’s” case, her lung mass was suspected to be a primary tumor, however she did not have abdominal radiographs or ultrasound to rule out the presence of an abdominal tumor. Regardless of the presence or absence of additional neoplastic disease, thoracic surgery would have been necessary to relieve her cough as well as her HO. Since at the time of presentation, her age and cachectic condition made her a poor surgical candidate, steroid treatment was started to ameliorate her discomfort from the HO. Despite this treatment, “Christy” returned to VESCONE 17 days after her initial presentation for euthanasia. The owner reported respiratory distress and continued weakness.

Reference:

Ettinger, SJ and Feldman, EC, Eds. Textbook of veterinary internal medicine. 5th edition, Pp 503, 1073-1078, 1903-1904

VIN Associate Data Base: http://www.vin.com/Members/Associate.plx?DiseaseID-468

Hara, Y; Tagawa, M; Ejima, H; et al. Regression of hypertrophic osteopathy following the removal of intrathoracic neoplasia derived from the vagus nerve in a dog. J Vet Med Sci 57(1)133-135 1995 (Abstract)