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REVIEW FOR RESIDENTS

The Solitary Pulmonary Nodule1

REVIEWS AND COMMENTARY

Helen T. Winer-Muram, MD

The imaging evaluation of a solitary pulmonary nodule is complex. Management decisions are based on clinical history, size and appearance of the nodule, and feasibility of obtaining a tissue diagnosis. The most reliable imaging features are those that are indicative of benignancy, suchas a benign pattern of calcification and periodic follow-up with computed tomography for 2 years showing no growth. Fine-needle aspiration biopsy and core biopsy are important procedures that may obviate surgery if there is a specific benign diagnosis from the procedure. In using the various imaging and diagnostic modalities described in this review, one should strive to not only identify smallmalignant tumors—where resection results in high survival rates— but also spare patients with benign disease from undergoing unnecessary surgery.
RSNA, 2006

1

From the Department of Radiology, Indiana University, Indianapolis, Ind. Received February 28, 2005; revision requested April 22; revision received April 28; accepted June 13; final version accepted August 11; final review and update by theauthor October 31. Address correspondence to the author, 11224 Clarkston Rd, Zionsville, IN 46077 (e-mail: hwinermu@iupui.edu). RSNA, 2006

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Radiology: Volume 239: Number 1—April 2006

REVIEW FOR RESIDENTS: The Solitary Pulmonary Nodule

Winer-Muram

A

solitary pulmonary nodule (SPN) is a round or oval opacity smaller than 3 cm in diameter that is completely surrounded bypulmonary parenchyma and is not associated with lymphadenopathy, atelectasis, or pneumonia (1) (Fig 1a). Larger lesions are not included in this definition because many of these lesions are malignant (2– 4). An SPN is noted on up to 0.2% of chest radiographs (5,6) (Fig 2a). While the differential diagnosis for SPN is extensive (Figs 3, 4), most lesions are found to be granulomas, lung cancers, orhamartomas (7,8) (Fig 5). Detection and work-up of SPNs are critical because SPNs may be malignant and lung cancer has an overall mortality rate of up to 85% (3,9). Early detection of small nodules may potentially reduce lung cancer–specific mortality; in time, data from the National Lung Screening Trial may be used to prove this hypothesis. While one may not be able to establish a diagnosis based solelyon the im-

aging features, the radiologist often plays a major role in the care of patients with SPNs. In this article, some of the clinical and radiographic features that are important to consider when determining the likelihood of malignancy of an SPN will be reviewed, and an algorithm will be proposed for the care of patients with indeterminate nodules.

Risk of SPN Malignancy
Tounderstand the rationale underlying clinical and imaging work-up when an SPN is discovered, one must first recognize the clinical factors that make lung cancer a more likely cause of SPN (Table). The likelihood of lung cancer increases if a patient has a smoking history, and it is directly proportional to the number of pack-years as a smoker (12). While many physicians have believed that smoking cessationproduces a progressive reduction in lung cancer incidence, this concept has been challenged (13). The incidence of lung cancer does not increase after smoking cessation, but it never equals that for individuals who have never smoked. Consequently, one commonly sees patients with newly diagnosed lung cancer who stopped smoking years or even decades earlier (14). Lung cancer risk also increases ifthe patient has a history of primary pulmonary or extrapulmonary cancer or pulmonary fibrosis (eg, idiopathic fibrosis or fibrosis due to asbestos exposure, collagen vascular disease, adult respiratory distress syndrome, or radiation) (10,15) (Fig 6). An SPN is unlikely to be a metastasis in the absence of a known prior malignancy, and a routine search for an extrathoracic primary tumor is not...
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