Solitary Pulmonary Nodule - Work-up

Work-up

The work-up in patients with a solitary pulmonary nodule is based on an initial risk assessment. If the risk of malignancy is thought to be low, follow-up imaging (usually serial CT scans) can be planned at a later time. The frequency of further scans can be determined by the patient's risk for cancer and the size of the nodule. If the initial impression is that there is a high likelihood of cancer, then a surgical intervention is appropriate (provided that the patient is fit for surgery).

If there is an intermediate risk of malignancy, further imaging with positron emission tomography (PET scan) is appropriate (if available). Around 95% of patients with a malignant nodule will have an abnormal PET scan, while around 78% of patients with a benign nodule will look normal on PET (this is the test sensitivity and specificity). Thus, an abnormal PET scan will reliably pick up cancer, but several other types of nodules (inflammatory or infectious, for example) will also show up on a PET scan. If the nodule has a diameter below 1 centimeter, PET scans are often avoided because there is an increased risk of falsely normal results. Cancerous lesions usually have a high metabolism on PET, as demonstrated by their high uptake of FDG (a radioactive sugar). If the lesion is found on further imaging to be suspicious, it should be surgically excised (via thoracotomy or video-assisted thoracic surgery) to confirm the diagnosis by microscopical examination.

In selected cases, nodules can also be sampled through the airways using bronchoscopy or through the chest wall using needle aspiration (which can be done under CT guidance). Needle aspiration can only retrieve groups of cells for cytology and not a tissue cylinder or biopsy, precluding evaluation of the tissue architecture. Theoretically, this makes the diagnosis of benign conditions more difficult, although rates higher than 90% have been reported. Complications of the latter technique include hemorrhage into the lung and air leak in the pleural space between the lung and the chest wall (pneumothorax). However, not all these cases of pneumothorax need treatment with a chest tube.

Other imaging techniques include PET-CT (simultaneous PET scan and CT scan with superposition of the images), magnetic resonance imaging (MRI) or single photon emission computed tomography (SPECT).