pulmonary disorders
Solitary Pulmonary Nodule
Evaluation of Solitary Pulmonary Nodule
The primary goal of evaluation is to detect cancer and active infection. History may reveal information that suggests malignant and nonmalignant causes of a solitary pulmonary nodule and includes Current or past cigarette smoking History of cancer or an autoimmune disorder Occupational risk factors for cancer (eg, exposure to asbestos, vinyl chloride, radon) Travel to, or living in, areas with endemic mycosis or a high prevalence of Tuberculosis (TB) (TB) Risk factors for opportunistic infections (eg, HIV, immune deficiency) Older age, cigarette smoking, and history of cancer all increase the probability of cancer and are used along with the nodule diameter to estimate likelihood ratios for cancer. A thorough physical examination may uncover findings that suggest an etiology (eg, a breast lump or skin lesion suggestive of cancer) for a pulmonary nodule but cannot definitely establish the cause. The goal of initial testing is to estimate the malignant potential of the solitary pulmonary nodule. The first step is a review of plain x-rays and then usually CT. Radiographic characteristicshelp define the malignant potential of a solitary pulmonary nodule: Growth rateis determined by comparison with previous chest x-ray or CT, if available. A lesion that has not enlarged in≥2 years suggests a benign etiology. Tumors that have volume doubling times from 21 to 400 days are likely to be malignant. Calcificationsuggests nonmalignant disease, particularly if it is central (tuberculoma, histoplasmoma), concentric (healed histoplasmosis), or in a popcorn configuration (hamartoma). Marginsthat are spiculated or irregular (scalloped) are more indicative of cancer. 5.3 cm strongly suggests cancer. However, nonmalignant exceptions include Lung Abscess , Location in the upper lobe carries a higher risk of malignancy. These characteristics are sometimes evident on the original plain film but usually require CT. CT can also distinguish pulmonary from pleural radiopacities. CT has a sensitivity of 70% and a specificity of 60% for detecting cancer. The mainstay of diagnosis of solitary pulmonary nodules is interval imaging. Specific imaging recommendations depend on the size of the nodule and whether the nodule is ground-glass, semi-solid, or solid, and individual risk factors (history of heavy smoking, exposure to asbestos, family history of lung cancer, older age [ Evaluation reference ]). Positron Emission Tomography (PET) None may be useful when historical information suggests an infectious cause (eg, TB, Coccidioidomycosis ) as a possible diagnosis. Invasive testingoptions include CT- or ultrasound-guided transthoracic needle aspiration Flexible bronchoscopy Surgical biopsy Although cancers can be diagnosed by biopsy, definitive treatment is resection, and so patients with a high likelihood of cancer with a resectable lesion should proceed to surgical resection. However, bronchoscopic endobronchial ultrasound-guided mediastinal lymph node biopsy is being used increasingly and is recommended by some experts as a less invasive way to diagnose and stage lung cancers before nodules are surgically resected. Transthoracic Needle Biopsy is best for peripheral lesions and is particularly useful if infectious etiologies are strongly considered because using the transthoracic approach, as opposed to bronchoscopy, avoids the possibility of contamination of the specimen with upper airway organisms. The main disadvantage of transthoracic needle aspiration is the risk of pneumothorax, which is about 10%. Flexible bronchoscopy allows for endobronchial washing, brushing, needle aspiration, and transbronchial biopsy. Yield is higher for larger, more centrally located lesions, but very experienced operators using specially designed thin scopes can successfully biopsy peripheral lesions that are<1 cm in diameter. In cases in which nodules are not accessible from these less invasive approaches, open surgical biopsy is necessary. 1.MacMahon H , Naidich DP, Goo JM: Guidelines for management of incidental pulmonary nodules detected on CT images: From the Fleischner Society 2017.Radiology284(1): Supplement, 2017. https://doi.org/10.1148/radiol.2017161659 