Lower Respiratory Tract Tumors

24 Lower Respiratory Tract Tumors

13. How do I obtain a sample for cytologic diagnosis?

Fine-needle cellular aspiration (blind or ultrasound-guided) is recommended even for dogs with diffuse pulmonary neoplasia. In most studies, it has been shown to be 80% to 90% successful in distinguishing a lung tumor from a nonmalignant cause and can be useful in identifying infectious agents as well. A specific cytologic diagnosis may be hindered by inflammation (nonseptic pyo- or pyogranulomatous inflammation) associated with lung neoplasms. Blind or guided fine-needle aspiration can be used to sample mass lesions and malignant pleural effusion. Pleural fluid obtained by percutaneous aspiration is often described as a modified transudate or exudate without evidence of neoplastic cells. Cytopathologic examination of tissue samples obtained by fine needle aspiration of the lung with a small-gauge (25 or 27 gauge, 1.5-inch needle on a 6-ml syringe is suggested) has been highly correlated with histopathologic examination of tissue obtained through thoracotomy. Cytopathologic diagnostic accuracy is improved with ultrasound guidance. Transthoracic fine needle aspiration is a minimally invasive procedure with rare to no adverse events reported after sampling. Many animals require no sedation or general anesthesia before a transthoracic fine needle aspiration.

When cutting core biopsy instruments are used to obtain a tissue sample (20 gauge Westcott needle, 18-20 gauge Menghini aspirate-biopsy needle [Tru-Cut]), complications are more frequent and potentially more severe. In one study, the overall diagnostic accuracy was 83%, but more than half of the animals had complications from the procedure. Asymptomatic pneumothorax was most common, and intrapulmonary hemorrhage, hemoptysis, and severe pneumothorax requiring removal of air were reported with rare deaths. Heavy sedation or general anesthesia is required. Transbronchial biopsy during bronchoscopic examination is seldom rewarding. Cytologic confirmation of neoplastic cells in fluid obtained from transtracheal wash or bronchoalveolar lavage is infrequently diagnostic, except in dogs with lymphoma.

Thoracotomy with lobectomy offers the opportunity for accurate histologic confirmation and is the also the treatment of choice for excisable tumors. Lymph node aspiration/biopsy can be obtained for clinical staging.

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Jul 31, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on Lower Respiratory Tract Tumors
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