An update on diagnosing and treating primary lung tumors - Veterinary Medicine
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An update on diagnosing and treating primary lung tumors
The incidence of this rare cancer in dogs and cats may be on the rise. Find out how to spot a primary lung tumor and what new forms of therapy may soon be at your disposal.



Because cats tend to have a higher incidence of poorly differentiated adenocarcinomas,10,16 it is not surprising that cats with primary lung tumors usually do not survive as long as dogs do. In a study of 21 cats treated with surgical resection, only histologic differentiation of the primary lung tumor had a significant correlation with survival time.27 Twelve cats with moderately differentiated tumors (57.1%) had a median survival time of 698 days, while nine cats with poorly differentiated tumors (42.9%) had a median survival time of 75 days. Although the study had inadequate power for statistical analysis of lymph node status, it did appear, as in dogs, that draining lymph node involvement may correlate with survival time, as 12 cats without enlarged tracheobronchial lymph nodes survived for a median of 412 days, whereas four cats with enlarged lymph nodes survived only a median of 73 days.27

In addition to histologic differentiation and lymph node enlargement, digital metastasis in cats with primary lung tumors is a poor prognostic finding. Cats with digital metastases have an average survival of 4.9 weeks (median 4 weeks) compared with a survival of 29.5 weeks (mean 12.5 weeks) in cats with primary digital squamous cell carcinoma.42


10. A lateral forelimb radiograph of a geriatric dog presented for evaluation of severe lameness and pain. Note the extreme periosteal proliferation consistent with hypertrophic osteopathy. The dog had a primary pulmonary carcinoma. (Photograph courtesy of Dr. Laura Garrett.)
In a retrospective study of 210 dogs with primary lung tumors, paraneoplastic syndromes were observed, but their frequency was low (< 6%): Six dogs had radiographic signs of hypertrophic osteopathy (2.9%) (Figure 10), two dogs were hypercalcemic, two dogs had a fever, and two dogs had tumor-induced secretion of adrenocorticotropic hormone (ACTH).4 From other investigations, the development of hypertrophic osteopathy in dogs with primary lung tumors has been reported to range from 4% to 17%.2,12 Overt lameness and pain in dogs with primary lung tumors may not always indicate hypertrophic osteopathy, as skeletal metastasis could also cause similar clinical signs of pain and discomfort. Other less frequent hematologic paraneoplastic syndromes associated with primary lung tumors in dogs include absolute erythrocytosis and leukocytosis.43,44

Paraneoplastic syndromes in cats occur even less frequently. In a study of 86 cats with primary lung tumors, none of the patients experienced paraneoplastic syndromes.16 Although lameness may be a common presenting sign (25% in one study), it is usually indicative of bone metastases rather than hypertrophic osteopathy.1 Single case reports of paraneoplastic syndromes have been suggested in cats, including marked leukocytosis in a cat with squamous cell carcinoma, hypercalcemia with bronchogenic adenocarcinoma, and thrombocytosis with bronchoalveolar carcinoma.45-47


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