Today I am showing radiographs of an asymptomatic 57-year-old man in whom a pulmonary nodule was discovered.
1. Probably benign
2. Probably malignant
4. It is extrapulmonary
Check the images below, leave your thoughts in the comments section, and come back on Friday for the answer.
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Findings: The nodule has a hazy lateral border (A, white arrow) because it is adjacent to the chest wall. The rounded shape goes against an extrapulmonary lesion, which should be more ovoid. The most relevant finding in the plain film is the presence of coarse calcification within the nodule (A, red arrow), which is a sign of benignancy. Coronal and axial CT confirm an intrapulmonary nodule with popcorn calcification (B and C, white arrows), as well as fat within the nodule (C, red arrow).
Final diagnosis: RUL hamartoma
I am presenting this case to review the second most common presentation form of lung carcinoma, a solitary pulmonary nodule (SPN), which occurs in up to 30% of cases. SPN is defined as a well- or poorly-defined rounded opacity, measuring up to 3 cm in diameter. A lesion larger than that is considered a mass, which is very likely malignant.
SPNs are not uncommon and are usually an incidental finding in chest radiographs. The main goal is to differentiate benign from malignant nodules as accurately as possible. In this presentation, I would like to share with you a few useful tips to approach the solitary pulmonary nodule in the plain chest radiograph.
Tip #1. Be sure to exclude pseudonodules before you start the work-up. Remember that up to 20% of suspected SPNs are false nodules, which may be transient or stable. Transient nodules are due to acute pulmonary conditions that simulate a nodular lesion (Figs. 1 and 2).
Stable pseudonodules are usually simulated by extrapulmonary structures, such as nipples, skin lesions, rib fractures, or bone islands (Figs. 3-5).
Tip #2. Pulmonary nodules are often missed. Be sure to look for them in the blind areas of the chest. Most are hidden in the upper lobes, where their reported miss rate is nearly 60% (Fig. 6).
Pulmonary nodules may hide in the central or peripheral areas in the PA radiograph (Fig. 7). Needless to say, the lateral view is crucial to detect SPNs hidden in the PA view (Fig. 8).
Tip #3. The most reliable criterion in plain films to determine our management of an SPN is whether or not it is growing in size. Therefore, it is essential to compare with previous films, when available. A nodule that has grown in the interval is probably malignant and should be acted upon (Fig. 9).
If no growth is evident over a period of 24 months, the nodule is likely benign and can be monitored by CT follow-up.
Tip #4. In plain films, visible calcium in an SPN is a reliable sign of benignancy (Fig. 11). This sign often fails because a high KV technique tends to “burn” the calcium, making it difficult to identify when present (Fig. 12).
As was mentioned earlier, a high kV technique tends to “burn” calcium, and even heavily calcified nodules may not be recognized in the plain radiograph. For this reason, CT should be performed when calcium is suspected and conventional radiography fails to demonstrate it (Fig. 13).
Follow Dr. Pepe’s advice:
1. Rule out pseudonodules before you start the work-up.
2. Search for missed nodules in blind areas of the chest, especially in the apices.
3. Look at previous films to determine whether or not a nodule is growing.
4. Detecting calcium in a nodule is a reliable sign of benignancy.