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How To Report S-modifiers And C-modifiers In Lung Cancer Screening

Incidental findings are common in lung cancer screenings with chest CT. However, reporting of the S-modifier or C-modifier within the Lung-RADs is often inconsistent. Below are some specific guidelines in order to improve reporting consistency and better define potential abnormalities.

Background On The Lung-RADS Reporting System

The American College of Radiology recommends using their Lung-RADS reporting system. When using this system, moderate to severe pulmonary calcifications must be reported as separate data points. The system requires radiologists to describe their findings on a 0–4 scale, along with a description of the lung nodules and their management. There are two additional categories: the “S” modifier, which is used to describe any “clinically significant or potentially significant findings,” and the “C” modifier, which is used if there is a prior history of lung cancer.

Confusion With The S-Modifier

The Lung-RADS reporting system defines the category “S” as occurring when a baseline screening reveals, “Other findings (non-lung cancer).” In this case, the “S,” “May add on to category 0–4.” The system defines category “1S” as occurring when a baseline screening reveals, “No nodules or nodules with calcification with other findings (non-lung cancer).”

The problem and potential confusion with these definitions are that the terminology “non-lung-cancer-related” is subject to interpretation and may not be used consistently.

To better understand this confusion and its potential reporting issues, a retrospective investigation was performed by the Stony Brook University Medical Center, which included 581 individuals who received a baseline low-dose chest CT for lung cancer screening. The study found that initially, “A total of 261 (45%) participants received the Lung-RADS S modifier on baseline CT with 369 incidental findings indicated as potentially clinically significant.” However, after investigation, “an additional 141 incidentalomas of the same types as these 369 findings were described in reports but were not labeled with the S modifier. Therefore, as high as 69% (402 of 581) of participants could have received the S modifier if reporting was uniform.”

How To Report Modifiers In A Radiology Report

Because of the potential confusion mentioned above, it is important to use as specific detail as possible. To improve accuracy and consistency below is an example of how we recommend reporting modifiers in a radiology report.

C Modifier

Prior history of lung cancer; CT exam result modifier C.

Select one:
N – No
Y – Yes
U – Unknown

S Modifier
Other clinically significant or potentially significant abnormalities; CT exam result modifier S.
Select one:
N – No
Y – Yes

If yes, what were the other findings?

Select all that apply:
0 – Aortic aneurysm
1 – Coronary arterial calcification moderate or severe
2 – Pulmonary fibrosis
3 – Mass (check neck, mediastinum, liver, kidneys, other)
4 – Other interstitial lung diseases

Why Reporting Consistency Matters

As screening becomes more widespread, accurate data registries will allow for additional efficiencies and improvements in the screening process. Also, reporting consistency will help fuel the advancement of a wide range of computer analytical tools that will provide information beyond just the early detection of lung cancer. Additionally, tracking other clinically significant findings showed an overall mortality benefit in the National Lung Screening Trial (NLST).

Eon’s Solution for Lung Cancer Screening uses the Lung-RADS guidelines to help lung cancer screening programs determine next steps for all eligible patients. Eon’s Solution for Incidental Pulmonary Nodules (IPN) helps identify, track and manage patients with IPNs based on the Fleischner Society guidelines. Together, Eon can provide an integrated solution for a comprehensive lung program.


Yankelevitz D, Henschke C. Advancing and Sharing The Knowledge Base of CT Screening For Lung Cancer. NCBI Website. Accessed September 16, 2018.

Mehta H, Mohammed TL, Jantz M. Reclassify Lung-RADS Category “S”. Chest Journal Website. Accessed September 16, 2018.

Reiter MJ, Nemesure A, Madu E, Reagan L, Plank A. Frequency and Distribution of Incidental Findings Deemed Appropriate for S Modifier Designation on Low-Dose CT in a Lung Cancer Screening Program. NCBI Website. Accessed September 16, 2018.

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