Finding a solitary pulmonary nodule on a chest x-ray is common and once detected, it needs to be evaluated promptly and managed because many such nodules can be malignant in nature. A large majority are picked up as asymptomatic lesions.
A solitary pulmonary nodule has been referred to as “coin” lesion, a nomenclature first devised by John Steel way back in the 60s. Some of its major characteristic features include solitary nature, circumscribed margins, diameter double the cross-sectional diameter of an adjacent blood vessel adjacent (1.5 cm), homogeneous density and completely surrounded by lung with no regional lymph node enlargement or satellite lesions.
There is a long list of conditions that are to be considered in the differential diagnosis of a solitary pulmonary nodule. The most common include lung cancer, benign lung tumor, tuberculoma, fungal granuloma, lung abscess and metastasis.
“Wait and Watch”, biopsy of the nodule or immediate thoracotomy are the management options. A thin slice CT (1 mm) is done to accurately describe the characteristics of the nodule and decision is taken on CT findings.
The updated 2017 Fleischner Society Guidelines for management of incidental pulmonary nodules detected on CT published in the July 2017 issue of the journal Radiology have recommended a range of time for follow-up CT scans, rather than a precise time period based on estimations of the individual risk of malignancy.
According to these guidelines, no routine follow-up is required for patients with a solid or subsolid (pure ground glass or part-solid) solitary pulmonary nodule <6 mm in low risk patients. While, no further diagnostic testing is recommended for patients with solid solitary pulmonary nodules that have remained stable over two years, or subsolid SPNs that have been stable over five years on serial CT scans.
A word of caution here. These recommendations do not apply to patients with known cancers at risk for metastases, immunocompromised patients, who are at risk of infections.
As these guidelines are Level 1 evidence, these recommendations should be followed (Evidence from a systematic review or meta-analysis of all relevant RCTs or evidence-based clinical practice guidelines based on systematic reviews of RCTs or three or more RCTs of good quality that have similar results).
1. Keerat Kaur Sibia et al. Chapter 46. How to manage solitary pulmonary nodule (SPN). Medicine Update. 2017. http://www.apiindia.org/pdf/medicine_update_2017/mu_046.pdf.
2. Gaude GS, et al. Evaluation of solitary pulmonary nodule. J Postgrad Med. 1995;41(2):56-9.
3. MacMahon H, et al. Guidelines for management of incidental pulmonary nodules detected on CT Images: From the Fleischner Society 2017. Radiology. 2017 Jul;284(1):228-243.