Malignancy estimation of Lung-RADS criteria for subsolid nodules on CT: accuracy of low and high risk spectrum when using NLST nodules

Eur Radiol. 2017 Nov;27(11):4672-4679. doi: 10.1007/s00330-017-4842-8. Epub 2017 Apr 24.


Purpose: Lung-RADS proposes malignancy probabilities for categories 2 (<1%) and 4B (>15%). The purpose of this study was to quantify and compare malignancy rates for Lung-RADS 2 and 4B subsolid nodules (SSNs) on a nodule base.

Methods: We identified all baseline SSNs eligible for Lung-RADS 2 and 4B in the National Lung Screening Trial (NLST) database. Solid cores and nodule locations were annotated using in-house software. Malignant SSNs were identified by an experienced radiologist using NLST information. Malignancy rates and percentages of persistence were calculated.

Results: Of the Lung-RADS 2SSNs, 94.3% (1790/1897) could be located on chest CTs. Likewise, 95.1% (331/348) of part-solid nodules ≥6 mm in diameter could be located. Of these, 120 had a solid core ≥8 mm, corresponding to category 4B. Category 2 SSNs showed a malignancy rate of 2.5%, exceeding slightly the proposed rate of <1%. Category 4B SSNs showed a malignancy rate of 23.9%. In both categories one third of benign lesions were transient.

Conclusion: Malignancy probabilities for Lung-RADS 2 and 4B generally match malignancy rates in SSNs. An option to include also category 2 SSNs for upgrade to 4X designed for suspicious nodules might be useful in the future. Integration of short-term follow-up to confirm persistence would prevent unnecessary invasive work-up in 4B SSNs.

Key points: • Malignancy probabilities for Lung-RADS 2/4B generally match malignancy risks in SSNs. • Transient rate between low-risk Lung-RADS 2 and high-risk 4B lesions were similar. • Upgrade of highly suspicious Lung-RADS 2 SSNs to Lung-RADS 4X might be useful. • Up to one third of the benign high-risk Lung-RADS 4B lesions were transient. • Short-term follow-up confirming persistence would avoid unnecessary invasive work-up of 4B lesions.

Keywords: Lung cancer; Management; Pulmonary nodules; Screening; Subsolid.

MeSH terms

  • Databases, Factual
  • Early Detection of Cancer / methods
  • Female
  • Humans
  • Lung Neoplasms / diagnostic imaging*
  • Lung Neoplasms / pathology
  • Middle Aged
  • Multiple Pulmonary Nodules / diagnostic imaging
  • Multiple Pulmonary Nodules / pathology
  • Neoplasm Invasiveness
  • Probability
  • Radiographic Image Interpretation, Computer-Assisted / methods
  • Software
  • Tomography, X-Ray Computed / methods