Abstract
The solitary pulmonary nodule (SPN), a single intrapulmonary spherical lesion that is fairly well circumscribed, is a common clinical problem. About half of SPNs seen in clinical practice are malignant, usually bronchogenic carcinomas. Some nodules are primary tumors of other kinds or metastatic. Virtually all benign SPNs are tuberculous or fungal granulomas. The standard management of the SPN of unknown cause is prompt surgical removal unless benignity is established by prior chest roentgenograms showing that the nodule has been stable (i.e., showing no growth) for 2 years or by the presence of a "benign" pattern of calcification. Less universally accepted criteria for benignity include (1) transthoracic needle aspiration biopsy (TNAB) showing a specific benign process, and (2) patient's age under 30 to 35 years. Bronchoscopy has a low diagnostic yield, particularly for benign nodules. SPNs usually grow at constant rates, expressed as the "doubling time" (DT). A nodule with a DT between 20 and 400 days is usually malignant. Benign nodules usually have a DT greater than 400 days. The prospective determination of DT by serial chest roentgenograms (the "wait and watch" strategy) is widely criticized but has clinical utility in special circumstances, particularly if the likelihood of malignancy is low and/or the anticipated surgical mortality is high. The presence and pattern of calcification are best shown by high-resolution thin-section computed tomography (CT). Diffuse, laminated, central or "popcorn" patterns of calcification indicate benignity. An eccentric calcium deposit or a stippled pattern does not rule out malignancy. CT densitometry will often show "occult" calcification in nodules that show no direct visual evidence of calcium deposition. The characteristics of the edge of the nodule correlate with the likelihood of malignancy. Nodules with irregular or spiculated margins are almost always malignant. The probability that the nodule is malignant (pCA) is related to the age of the patient, the diameter of the nodule, the amount of tobacco smoke inhalation, the overall prevalence of malignancy in SPNs, the nature of the edge of the lesion, and the presence or absence of occult calcification. It is possible by Bayesian techniques to combine these factors to calculate a more precise and comprehensive prediction of pCA in any given nodule. The 5-year survival after nodule resection depends on the size of the nodule at the time of surgery; it may be as high as 80% with nodules that are 1 cm in diameter. Lymph node involvement is uncommon with small tumors, and many authorities question the need for CT staging in such cases.(ABSTRACT TRUNCATED AT 400 WORDS)
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