Veterinary Medicine - March 2008 - (Page 160)

Primary lung tumors PEER-REVIEWED 25% of cats presented with lameness, likely resulting from digital skeletal metastasis associated with primary pulmonary carcinoma. Respiratory signs were noted in only one-third of the cats, and coughing was rarely reported.1 In contrast, another feline study found that all 86 cats had at least one clinical sign directly or indirectly related to their primary lung tumor, and 53 of the cats (61.6%) had signs of respiratory dif culty.16 In general, cats with primary lung tumors present with a wide range of clinical ndings, and the absence of overt pulmonary signs should not preclude a primary lung tumor as a differential diagnosis. are considered a high-yield diagnostic test, often revealing a pulmonary mass when present.16 Differential diagnoses for pulmonary masses include primary lung tumors (77% in one study), granulomas, cysts, abscesses, infarcts, diaphragmatic hernias, and metastatic neoplasia.4,29 Cytology Although the most accurate way to de nitively diagnose a pulmonary mass is through surgery and histologic examination, other less-invasive diagnostic techniques, such as cytology, may be attempted rst. Fine-needle aspiration appears to be the safest and most convenient method of harvesting cytologic samples for initial diagnosis (Figure 3). A recent study comparing cytologic and histologic diagnosis of pulmonary neoplasia revealed that cytologic samples retrieved with 25- to 27-ga needles showed agreement with histologic diagnosis in 82% of cases, with 100% speci city and 77% sensitivity.30 As would be expected, cytologic accuracy for diagnosing neoplasia is higher with ultrasound guidance vs. blind aspiration, as visualization of the suspect primary lung tumors is necessary to maximize appropriate sample collection (Figure 4).30 Fluoroscopy also facilitates the accurate and ef cient retrieval of cellular samples from suspect pulmonary tumors.31 Although ne-needle cytology with small-gauge needles (25 to 27 ga) appears safe and relatively accurate, studies using large-gauge needles (18 to 21 ga) demonstrate even greater correlation between cytologic and histologic results collected from suspect lung lesions.32 However, despite a higher cellular yield, the complication rate using 18- to 21-ga needles is reported to be 46%, with a fatality rate of 15%.32 In contrast, no substantial complications have been reported with using 22- to 25-ga needles in companion animals for retrieving cytologic samples from lung parenchymal lesions.33 Furthermore, in a recent human study no signi cant difference was identi ed in diagnostic DIAGNOSIS Primary pulmonary neoplasms are usually an incidental nding in animals presented for general health checks or evaluation of nonspeci c signs. Thoracic radiography is often the initial step in evaluating patients with respiratory disease, but radiographic patterns are not speci c for a single disease process so further diagnostic tests are necessary. Thoracic radiography The appearance of primary lung tumors varies from a solitary mass (Figure 1) to involvement of an entire lung lobe or multiple lobes (Figure 2), indicating metastatic disease or multicentric pulmonary tumors. Radiographic assessment may be confounded by atelectasis secondary to pneumothorax or pleural effusion. Pleural effusion may result from regional lymph node metastasis, extension of the tumor into the pleura, or concurrent disease such as congestive heart failure or other nonneoplastic processes such as hypertrophic cardiomyopathy, feline infectious peritonitis, and chylothorax.1,14 But keep in mind that pleural effusion devoid of neoplastic cells on cytologic examination does not necessarily rule out primary pulmonary neoplasia.14,19,28 In most patients without pleural effusion or severe concurrent thoracic disease, survey thoracic radiographs 160 March 2008 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - March 2008

Veterinary Medicine - March 2008 Contents Toxicology Brief Idea Exchange A Challenging Case An Update on Diagnosing and Treating Primary Lung Tumors CE Form Product Preview Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - March 2008

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