Fleischner Criteria

November 2005 Radiology, 237, 395-400

Fleischner Criteria for follow up of Incidental solid nodules on CT


  Patient Risk               LOW Risk Patient                       HIGH Risk Patient (Smoker)

Initial or
F/U Scan -->
   Initial        F/U        Initial       F/U

Nodule Size






 <4 mm




12 mo


   4 – 6mm

12 mo



6-12 mo

18-24 mo

   6 – 8mm

6-12 mo

12 mo x 1


3-6 mo

6, then 12 mo
if stable






>8 mm

Follow up CT at 3,9 and 24  mo with Enhanced CT, vs PET or Biopsy


Note: For Ground glass densities, see below, or follow link for more information.  They may require longer follow up to exclude indolent malignancy.

Figure 4:
Illustration of the relationship between the Noguchi histologic classification of adenocarcinoma of the lung (Noguchi types A though F) and corresponding CT appearances of these lesions. As denoted by the large arrow on the right, there is also good correlation between CT appearances and worsening prognosis progressing through the Noguchi classification A to F.


Suggested Guidelines in the Management of Subsolid Nodules

Incidentally identified, isolated pure GGOs smaller than 5 mm in size represent foci of AAH sufficiently often to obviate routine follow-up CT studies, especially in the elderly. Although it is acknowledged that some of these lesions may prove to be BAC, the extreme rarity of invasive adenocarcinomas in this subgroup coupled with their extremely prolonged doubling times suggest that there is no reason to undergo either the added expense or radiation exposure necessary to follow these lesions presumably over prolonged time intervals measured in years. An exception is patients enrolled in low-dose lung cancer screening programs for which follow-up imaging is presumably dictated by protocol.
Given that the uncertainty regarding the above issues will likely persist for the foreseeable future, by using currently available data, the following interim guidelines are proposed. These do not differentiate between low- and high-risk group as per Fleischner criteria (85) due to the increased incidence of adenocarcinomas in younger and nonsmoking patients. It cannot be overemphasized that these guidelines need to be interpreted in the light of individual clinical history.

Lesions Smaller than 10 mm with Pure GGO

Isolated lesions smaller than 5 mm in size with pure GGO represent foci of AAH sufficiently often to obviate follow-up CT studies.
Conservative management of nodules between 5 and 10 mm in size with pure GGO requires at least an initial follow-up examination in 3–6 months to document that lesions have not resolved spontaneously (or following antibiotic therapy). Although a small percentage of these lesions will prove to be invasive adenocarcinomas, the role of surgical biopsy in these cases remains problematic with appropriate management, necessitating case by case evaluation. For most of these lesions, continued long-term follow-up is likely preferable to surgical resection.
When opted for, follow-up surveillance should extend for more than 2 years. As the optimal duration of follow-up of lesions with pure GGO has yet to be determined, at least three consecutive annual studies is a minimum requirement to document stability. The need for further follow-up examinations remains speculative: While the number of lesions that enlarge or increase in attenuation later than 3 years is small, a sufficient number evolve to justify extended surveillance. In our experience, it was for as long as 5 years, although it cannot be overemphasized that the risk of subsequent development of cancer clearly needs to be balanced against the risks of unnecessary radiation exposure and especially surgical intervention (86).
Accurate assessment of interval change is best accomplished by comparing thin-section CT scans, allowing as precise comparison as possible to minimize both inter- and intraobserver variability in measurements, as well as close monitoring of any change in the attenuation of lesions, as either change should be interpreted as indicative of possible malignancy, in most cases necessitating surgical resection.
PET or PET/CT scans are of questionable diagnostic value or may even be misleading in the majority of cases of lesions smaller than 1 cm in diameter and should not be routinely obtained, especially given the small likelihood of associated metastatic disease rendering the potential use of PET for staging less useful.
Transbronchial aspiration should be discouraged as unlikely to provide sufficient data to either accurately assess malignant potential or establish a benign diagnosis. Instead, core needle biopsy should be preferentially performed, especially in cases for which surgery is contraindicated and histologic evaluation is deemed necessary.
In all cases in which follow-up surveillance is undertaken, subsequent CT studies should be performed with the lowest possible exposure techniques to minimize radiation exposure in these patients. In our experience, studies performed with as low as 80 mAs (depending on body habitus) are of sufficient quality to allow accurate follow-up assessment of these lesions.

Solitary Lesions 10 mm or Larger in Size with GGO

As a general rule, solitary lesions 10 mm or larger in size with pure GGO should be resected, provided that persistence or growth of the lesion is again established over at least a 3–6-month period. In this setting, indications for percutaneous needle biopsy are still limited as the likelihood of a definitive histologic diagnosis remains problematic given substantial sampling error. Similarly, indications for PET or PET/CT remain doubtful as PET-negative studies do not exclude the possibility of invasive adenocarcinoma, while these lesions are also still unlikely to be associated with distant metastases.

Lesions with Mixed Solid Component and GGO

Similar to solitary lesions 10 mm or larger in size with GGO, any lesion with mixed solid component and GGO, regardless of size, represents malignancy with sufficient likelihood to warrant further evaluation. The evaluation should include the timely performance of PET or preferably PET/CT, since there is a greater likelihood that these lesions represent invasive tumors for which preoperative staging and assessment of prognosis is warranted. Less clear is the role for transbronchial and/or transthoracic biopsy in these cases, given the limited value of accurate differentiation between BAC and invasive adenocarcinomas, especially for lesions with less than 50% solid components, and the likelihood that these lesions will be resected, regardless.

Multiple Subsolid Nodules

In cases of multiple lesions smaller than 5 mm with pure GGO, at least 1-year follow-up surveillance CT study should be performed on the premise that these patients may be at greater risk than the general population for developing cancer. However, continued long-term follow-up should not be considered necessary.
In general, follow-up CT surveillance is to be preferred in cases in which multiple small (5–10-mm in size) lesions are identified, as these most likely represent either multifocal AAH or in smokers, respiratory bronchiolitis.
In distinction, (a) surgical resection should be considered, especially in cases in which there are dominant lesions, defined as GGOs greater than 10 mm in size or lesions with mixed solid component and GGO; (b) PET or preferably PET/CT should be performed following a similar logic as outlined above for solitary lesions with mixed solid component and GGO; and (c) limited lung-sparing resections may be considered as an option to routine lobectomy given the likelihood that at least some of the remaining lesions will continue to grow.
In conclusion, new appreciation of the importance of subsolid nodules has led to the need for a reappraisal of the natural history of such lesions. While numerous controversial aspects remain, the main purpose of this report has been to set out interim guidelines based on best-guess estimates, the authors' extensive albeit anecdotal experience, and especially currently available published data. It cannot be overemphasized that the guidelines proposed in this review pertain to subsolid nodules only and are not intended to supplant guidelines regarding the management of solid nodules that have already been published both as a consensus statement of the Fleischner Society (85) and more recently by the American College of Chest Physicians (87).
It is anticipated that future developments based on multidisciplinary efforts will result in greater consensus regarding optimal CT classification of subsolid lesions and ultimately more definitive, evidence-based guidelines leading to more rigorous standardization and ultimately improved clinical treatment of patients with subsolid lung nodules.