A Veteran With a Solitary Pulmonary Nodule

Case Presentation. A 69-year-old veteran presented with an intermittent, waxing and waning cough. He had never smoked and had no family history of lung cancer. His primary care physician ordered a chest radiograph, which revealed a nodular opacity within the lingula concerning for a parenchymal nodule. Further characterization with a chest computed tomography (CT) demonstrated a 1.4-cm left upper lobe subpleural nodule with small satellite nodules (Figure 1). Given these imaging findings, the patient was referred to the pulmonary clinic.

►Lauren Kearney, MD, Medical Resident, VA Boston Healthcare System (VABHS) and Boston Medical Center. What is the differential diagnosis of a solitary pulmonary nodule? What characteristics of the nodule do you consider to differentiate these diagnoses?

►Renda Wiener, MD, Pulmonary and Critical Care, VABHS, and Assistant Professor of Medicine, Boston University School of Medicine. Pulmonary nodules are well-defined lesions < 3 cm in diameter that are surrounded by lung parenchyma. Although cancer is a possibility (including primary lung cancers, metastatic cancers, or carcinoid tumors), most small nodules do not turn out to be malignant.¹ Benign etiologies include infections, benign tumors, vascular malformations, and inflammatory conditions. Infectious causes of nodules are often granulomatous in nature, including fungi, Mycobacterium tuberculosis, and nontuberculous mycobacteria. Benign tumors are most commonly hamartomas, and these may be clearly distinguished based on imaging characteristics. Pulmonary arteriovenous malformations, hematomas, and infarcts may present as nodules as well. Inflammatory causes of nodules are important and relatively common, including granulomatosis with polyangiitis, rheumatoid arthritis, sarcoidosis, amyloidosis, and rounded atelectasis.

To distinguish benign from malignant etiologies, we look for several features of pulmonary nodules on imaging. Larger size, irregular borders, and upper lobe location all increase the likelihood of cancer, whereas solid attenuation and calcification make cancer less likely. One of the most reassuring findings that suggests a benign etiology is lack of growth over a period of surveillance; after 2 years without growth we typically consider a nodule benign.¹ And of course, we also consider the patient’s symptoms and risk factors: weight loss, hemoptysis, a history of cigarette smoking or asbestos exposure, or family history of cancer all increase the likelihood of malignancy.

►Dr. Kearney. Given that the differential diagnosis is so broad, how do you think about the next step in evaluating a pulmonary nodule? How do you approach shared decision making with the patient?

►Dr. Wiener. The characteristics of the patient, the nodule, and the circumstances in which the nodule were discovered are all important to consider. Incidental pulmonary nodules are often found on chest imaging. The imaging characteristics of the nodule are important, as are the patient’s risk factors. A similarly appearing nodule can have very different implications if the patient is a never-smoker exposed to endemic fungi, or a long-time smoker enrolled in a lung cancer screening program. Consultation with a pulmonologist is often appropriate.

It’s important to note that we lack high-quality evidence on the optimal strategy to evaluate pulmonary nodules, and there is no single “right answer“ for all patients. For patients with a low risk of malignancy (< 5%-10%)—which comprises the majority of the incidental nodules discovered—we typically favor serial CT surveillance of the nodule over a period of a few years, whereas for patients at high risk of malignancy (> 65%), we favor early surgical resection if the patient is able to tolerate that. For patients with an intermediate risk of malignancy (~5%-65%), we might consider serial CT surveillance, positron emission tomography (PET) scan, or biopsy.¹ The American College of Chest Physicians guidelines for pulmonary nodule evaluation recommend discussing with patients the different options and the trade-offs of these options in a shared decision-making process.¹