Page 532 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

510 PART IV Specific Malignancies in the Small Animal Patient

noted on CT and tumor type was identified, but intrapulmo- 38% to 90% of cases. 281–283 Diagnosis of primary pulmonary
nary metastasis detected by CT was common, being noted in neoplasia in cats is reportedly higher with 80% to 100% of cases
265,286,322
288
being diagnosed by FNA and cytology.
53% of cats.

VetBooks.ir racic radiographs in the assessment of tracheobronchial LN
Thoracic CT has been shown to be more accurate than tho-
metastasis. 284 In 14 dogs with primary pulmonary tumors, the Pretreatment Biopsy
accuracy of CT to determine tracheobronchial LN metasta- A pretreatment biopsy (biopsy performed before definitive
sis was 93% compared with 57% for thoracic radiography. 284 therapy) can be performed before lung lobectomy, although the
Additionally, five dogs deemed to be free of pulmonary metas- clinical relevance is questionable. 324 A pretreatment biopsy may
tasis with thoracic radiographs were found to have pulmonary be considered if histologic grade or degree of differentiation is
metastasis with CT. 284 In a separate study evaluating CT charac- required before an owner is willing to consider lung lobectomy
teristics of tracheobronchial LN metastasis, 16 of 18 dogs were or there is suspicion that a pulmonary neoplasm is not a pri-
diagnosed with primary pulmonary tumors and these dogs were mary tumor (i.e., either metastatic or systemic neoplasia such
compared with 10 normal dogs. 315 Metastatic disease to LN was as lymphoma). However, if the eventual goal is to remove the
significantly more likely when a transverse maximum LN diam- pulmonary tumor with a lung lobectomy, then a pretreatment
eter of 12 mm or LN-to-thoracic body ratio of 1.05 were used as biopsy is unnecessary because the biopsy result will not change
cutoffs. 315 Additionally, LN heterogenous and/or ring contrast the surgical recommendation or the owner’s willingness to treat.
enhancement patterns were significantly related to metastatic Multiple techniques for performing a pretreatment biopsy have
disease. 315 been described, including utilizing a biopsy needle, broncho-
In a study evaluating the assessment of pulmonary metastatic scopic biopsy, keyhole incision with staple application, and
disease in 18 dogs (two of which had bronchoalveolar carcinoma) thoracoscopy. 265,281,283,307,323–325
by thoracic radiography and CT, only 9% of CT-detected pul- Sedation or anesthesia is required to perform a pretreat-
monary nodules were noted on thoracic radiographs. 316 CT was ment needle-core biopsy. The use of ultrasound-, fluoroscopic-
able to detect pulmonary nodules as small as 1 mm, whereas the or CT-guidance is recommended to improve targeting of the
smallest lesions detected with thoracic radiography were 7 to 9 lesion and decrease the risk of iatrogenic trauma to normal
mm. 316 Overall, CT was significantly more sensitive than thoracic structures. 313,323,324 In a study of dogs and cats undergoing CT-
radiography in the identification of pulmonary nodules. 316 In a guided tissue-core biopsies of intrathoracic lesions (including
separate study, CT was able to detect a greater amount of nodules pulmonary tumors), the diagnostic accuracy was 92% and the
compared with computed and film-screen radiography. 317 Addi- sensitivity for diagnosing neoplasia was 80%. 323 A procedural
tionally, CT was better at identifying smaller nodules and was complication rate of 43% was reported with pulmonary hem-
associated with greater diagnostic confidence and observer accu- orrhage (30%) and pneumothorax (27%) the most common
racy and agreement. 317 complications. 323
Bronchoscopic biopsy has been performed in dogs and cats
Other Imaging Modalities with pulmonary neoplasia with mixed success. 265,283 Broncho-
scopic findings in patients with primary pulmonary neoplasia
The use of positron emission tomography (PET) is uncommon include narrowing of bronchi, mucosal erosions, and mucosal
in veterinary patients, but some early data regarding its use are swelling and hyperemia. 326 In one series of seven cats, five cats
available. 318–320 In one report, 18 fluorodeoxyglucose ( FDG) were successfully diagnosed by means of endoscopic bronchiolar
18
was administered as a radiotracer to evaluate a dog with pulmo- brushing. 265
18
nary nodules. Increased FDG uptake was noted in four nod- A keyhole lung biopsy technique has been described for non-
ules and these were identified as pulmonary adenocarcinoma at neoplastic lung disease. 307 For this technique, a lung biopsy is
necropsy. 319 obtained via a small thoracotomy (3–7 cm) with a surgical stapler
Near-infrared (NIR) imaging was recently evaluated in eight applied across the lung lobe to seal vessels and small airways. 307
dogs with primary pulmonary tumors. 321 In this study, pulmonary Thoracoscopy is a minimally invasive surgical option to obtain
tumors and normal lung were both imaged. In situ, the tumor a pretreatment biopsy. 327 In a study describing the use of tho-
was easily pinpointed with NIR imaging and all eight tumors racoscopy to determine the cause of pleural effusion in 18 cats
appeared equally fluorescent to the surgeon. 321 An additional and dogs, biopsies of several suspicious intrathoracic lesions were
interesting finding was that NIR imaging was able to accurately performed. 328 In eight cases, neoplasia was the cause of the pleu-
distinguish normal lung parenchyma from neoplastic tissue, but ral effusion, although the number of primary pulmonary tumors
could not distinguish peritumoral inflammation from neoplastic resulting in pleural effusion was unknown. 328 Thoracoscopy pro-
tissue. 321 The intraoperative use of NIR imaging modality may vided a means to both biopsy lung lesions and explore the thoracic
better facilitate tumor resection. cavity. 328
Differentiating poorly differentiated primary lung tumors from
Fine-Needle Aspiration metastatic lesions can occasionally provide a diagnostic challenge,
particularly when evaluating cytology. Immunohistochemistry or
FNA of a pulmonary mass may be performed before lung lobec- possibly immunocytochemistry using antibodies directed against
tomy to attempt to obtain a cytologic diagnosis. FNA is often per- thyroid transcription factor-1, cytokeratin, vimentin, or others
formed with ultrasound- or CT-guidance; however, blind aspirates may be useful in differentiating primary lung tumors from meta-
have been reported. 265,313,322,323 Sedation is generally required to static disease. 329–332 Antibodies against CD18 and CD204 may
prevent iatrogenic trauma during the aspiration process. In dogs, also be useful for differentiating pulmonary tumors of histiocytic
preoperative FNA with cytology has resulted in a diagnosis in origin. 333–335