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).
Source
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.
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