Pulmonary Nodules



Pulmonary Nodules






21.1 Solitary Nodule

By definition, a pulmonary nodule is a rounded opacity in the lung parenchyma measuring up to 3 cm. It is surrounded by aerated lung parenchyma and is smoothly marginated, with no adjacent atelectasis or associated lymphadenopathy.1 This presents a common diagnostic dilemma in the clinical setting.

A large variety of benign and malignant diseases cause pulmonary nodules. ▶Table 21.1 gives an overview of the histologic entities that can manifest as a pulmonary nodule.



21.1.2 Management

Nodules identified as incidental findings on chest radiography often measure more than 1 cm and should be further investigated since they are viewed as potentially malignant until proven otherwise.12 In general, CT is the next diagnostic modality indicated, with two exceptions that need no further investigation:



  • If previous images show at least 2-year nodule stability.


  • If an extrapulmonary location of the nodule is suspected (e.g., mammillary shadows or rib osteoma; this can be further explored on chest radiography using mammilla markings or rotational fluoroscopy, thus with markedly lower radiation exposure than on CT). CT is often able to visualize small, incidentally detected, nodules not found
    on chest radiography or only identifiable retrospectively in relation to the CT findings. Several lung cancer screening studies with low-dose CT have already produced extensive data on the potential malignancy of incidentally detected nodules. At least one nodule was identified on CT in up to two-thirds of all study participants at high risk for lung carcinoma. The majority of these nodules were very small. In all studies, more than 95% of these pulmonary nodules proved to be benign.


Growth exclusion is a good predictor of nodule benignity. Two-year stability of solid pulmonary nodules (of soft-tissue density) is generally accepted as a benignity criterion. Subsolid nodules can prove to be a slowly growing adenocarcinoma even after 2-year stability and therefore must be followed up beyond that period up to 5 years.13

Management of pulmonary nodules depends on their likelihood of malignancy and the expected growth pattern. Because the latter differs between solid and subsolid nodules, recommendations vary dependent on nodule attenuation as described below.

Several recommendations for management of incidental pulmonary nodules have been published, starting with the first recommendation for management of solid nodules of the Fleischner Society in 2005,14 followed by a recommendation for management of subsolid nodules in 2013.15 The newest recommendation from 2017 includes recommendations for solid and subsolid nodules and will be presented in more detail below.13


Solid Nodules

If the benignity of a nodule can be demonstrated on the basis of the listed criteria, there is no need for further measures. In all other cases, the choice of further procedure will depend on the nodule size and presence of risk factors.








Table 21.2 Recommendations for CT follow-up intervals and management of solid pulmonary nodules that do not meet benignity criteria depending on mean nodule diameter (average of long and short axis, rounded to the nearest millimeter) or nodule volume13

































Nodule type


Risk


<6 mm (<100 mm3)


6-8 mm (100-250 mm3)


>8 mm (>250 mm3)


Single


Low


No routine follow-up


6-12 months, consider 18-24 months


3 months or PET or tissue sampling


High


Optional 12 months


6-2 months, 18-24 months


3 months or PET or tissue sampling


Multiple


Low


No routine follow-up


3-6 months, consider 18-24 months



High


Optional 12 months


3-6 months, 18-24 months



Note: High risk: at least one risk factor (see above); low risk: no such known risk factor.



Table 21.2 lists the recommended procedure for nodules measuring less than 8 mm in relation to diameter size and risk of malignancy13:



  • Nodules with a mean diameter (average of longest diameter and diameter perpendicular to the longest diameter, rounded to the nearest full millimeter) of less than 6 mm in patients with no risk factors have such a low risk of malignancy that no further investigation or follow-up is recommended. In persons with known risk factors or if the nodule looks morphologically suspicious, a 12-month follow-up CT scan can be performed.


  • If a decrease in the size of a nodule has been observed during follow-up or the nodule disappears completely, follow-up is no longer required. Nodule benignity is just about proven.


  • If there is evidence of nodule stability, follow-up is advisable at variable intervals tailored to the individual risk.


  • Progressive growth of a nodule during follow-up is suggestive of malignancy and normally needs further investigation (histologic confirmation).

Nodules measuring more than 8 mm have a markedly higher risk of malignancy than smaller pulmonary. Hence, further
diagnostic work-up should be considered. A multidisciplinary decision on necessary diagnostic measures is recommended, with pneumonologists and thoracic surgeons taking into consideration the aspects listed in ▶Table 21.3. There is no need for further invasive investigation if malignancy appears unlikely in the context of the described morphology criteria. This may also apply in the individual case if PET or contrast dynamic CT yield a negative result.

In principle, patients with equivocal or suspicious nodules measuring more than 8 mm should be referred to a specialist center where radiologists, pneumologists, thoracic surgeons, and radiotherapists can take a multidisciplinary decision on the choice of procedure. That decision is based on several aspects:

Apr 12, 2020 | Posted by in CARDIOVASCULAR IMAGING | Comments Off on Pulmonary Nodules

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