pulmonary disorders
Lung Carcinoma
Diagnosis of Lung Carcinoma
Chest x-ray CT or combined positron emission tomography (PET)–CT Cytopathology examination of pleural fluid or sputum Bronchoscopy-guided or percutaneous transthoracic biopsy and core biopsy Sometimes surgical lung biopsy is often the initial imaging test. It may show clearly defined abnormalities, such as a single mass, multifocal masses, a Solitary Pulmonary Nodule , an enlarged hilum, a widened mediastinum, tracheobronchial narrowing, atelectasis, nonresolving parenchymal infiltrates, cavitary lesions, or unexplained pleural thickening or effusion. These findings are suggestive but not diagnostic of lung cancer and require follow-up with CT scans or combined PET–CT scans and cytopathologic confirmation. shows many characteristic anatomic patterns and appearances that may strongly suggest the diagnosis. If a lesion found on a plain x-ray is highly suggestive of lung cancer (ie, based on risk factors such as age, tobacco use, symptoms), PET–CT may be done to assist in directing the diagnostic evaluation and Staging . This study combines anatomic imaging from CT with functional imaging from PET. The PET images can help differentiate inflammatory and malignant processes. Both CT and PET–CT can help direct core needle biopsy of lesions not amenable to bronchoscopic biopsy. These PET images may also detect regional or distant metastatic disease. The method used to obtain cells or tissue for confirmation depends on the accessibility of tissue and the location of lesions. Cytology of a sputum or pleural fluid sample is the least invasive method to confirm lung cancer diagnosis. In patients with productive cough, sputum specimens obtained on awakening may contain high concentrations of malignant cells, but yield for this method is<50% overall. Pleural fluid is another convenient source of cells; a malignant effusion is a poor prognostic sign and indicates advanced stage disease. In general, false-negative cytology readings can be minimized by obtaining as large a volume of sputum or pleural fluid as possible early in the day (for sputum samples) and sending the sample to the pathology laboratory immediately to minimize delays in processing because such delays lead to cell breakdown. Molecular (genetic) studies can be done on paraffin-embedded tumor cell pellets from pleural fluid if the fluid is spun down and the cell pellet preserved in a timely fashion. is the next least invasive procedure. It is more useful for metastatic sites (eg, supraclavicular or other peripheral lymph nodes, pleura, liver, adrenals) than for lung lesions. Risks include a 20 to 25% chance of Pneumothorax (primarily in patients with significant emphysema) and the risk of obtaining a false-negative result. A core biopsy is preferable to a fine-needle biopsy because the latter retrieves too little tissue for accurate genetic studies. Bronchoscopyis the procedure most often used for diagnosing lung cancer. In theory, the procedure of choice for obtaining tissue is the one that is least invasive; however, in practice, bronchoscopy is often done in addition to or instead of less invasive procedures because diagnostic yields are greater and because bronchoscopy is also important for staging. A combination of washings, brushings, and biopsies of visible endobronchial lesions and of paratracheal, subcarinal, mediastinal, and hilar lymph nodes often yields a tissue diagnosis. Advances in techniques to guide the bronchoscope have increased the diagnostic yield and the accuracy of sampling more peripheral lesions. Endobronchial ultrasound-guided biopsy (EBUS) can be done during bronchoscopy and has an excellent yield. EBUS is currently the preferred method for staging the mediastinum, except in cases where the lymph nodes cannot be sampled due to anatomic considerations. Navigational bronchoscopy is also used to sample more peripheral lesions with improved diagnostic accuracy. Robotic bronchoscopy is also being implemented at certain centers to improve the diagnostic yield and limit the number of thoracic surgical procedures. Mediastinoscopyhad been the standard test for evaluating mediastinal lymph nodes but is a higher risk procedure that is typically used before more extensive thoracic surgical procedures to confirm or exclude the presence of tumor in those few patients with enlarged mediastinal lymph nodes that cannot be sampled by EBUS. done via Thoracoscopy and Video-Assisted Thoracoscopic Surgery , is indicated when less invasive methods do not provide a diagnosis in patients whose clinical characteristics and radiographic features strongly suggest that the tumor is resectable. 