Keywords:
CT, Thorax, Decision analysis, Cancer, Outcomes
Authors:
D. Dressler1, D. J. Borgaonkar2, K. Greenlaw1, D. Manos3; 1Halfiax/CA, 2Halifax/CA, 3Halifax, NS/CA
DOI:
10.26044/esti2019/P-0095
Background
Tiny pulmonary nodules are less than 6mm in diameter
A pulmonary nodule is a rounded opacity in the lung parenchyma measuring 3 cm or less in diameter (1).
The adjective small has been used to describe nodules that are less than 1 cm in diameter and tiny for pulmonary nodules less than 6 mm in diameter (1).
Tiny pulmonary nodules are best demonstrated on thin section (1 to 2 mm collimation) CT.
Thicker section imaging may cause a small solid nodule to be missed or artifactually appear as a ground glass density.
Tiny pulmonary nodules are very common and are rarely malignant
Tiny pulmonary nodules are a common incidental finding on chest CT. The prevalence of noncalcified pulmonary nodules in participants of lung cancer screening trials ranges from 41-74% (2-8). Approximately 10% of never-smokers have pulmonary nodules (9).
Pulmonary nodules have clinical significance because they occasionally can be an early manifestation of lung cancer,
a leading cause of cancer death.
However,
the vast majority of tiny pulmonary nodules are benign.
A solid baseline nodule under 6 mm,
even in a patient at high clinical risk (smoker or former heavy smoker),
confers a very low probability of malignancy of approximately 0.1-0.6% (2,
4,
10).
Pulmonary nodules have a variety of causes.
Often they are the result of a previous infectious or inflammatory process.
Infection including fungal,
bacterial or mycobacterial,
can result in the formation of granulomas which can calcify over time.
Non-infectious inflammatory causes may include sarcoidosis or inhalation of irritant substances such as tobacco smoke.
Perifissural nodules often represent intrapulmonary lymph nodes and have a characteristic morphology.
Occasionally a tiny pulmonary nodule can prove to represent malignancy [figures 1-13].
Predicting risk of lung cancer is important because early diagnosis can lead to definitive treatment.
If identified at an early stage,
surgical resection of non-small cell lung cancer offers a favourable prognosis with 5-year survival rates of up to 70% for small,
localized tumours (stage 1).
On the other hand,
the prognosis remains poor for patients who have advanced disease at time of diagnosis (stage 3 and 4) (11).