Limited life expectancy and/or significant comorbidities
Patient Age
Age < 35 years
Age ≥ 35 years
Nodule Size (largest dimension)
cm
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Reference: Hoang JK, Langer JE, Middleton WD, et al. Managing Incidental Thyroid Nodules Detected on Imaging: White Paper of the ACR Incidental Thyroid Findings Committee.
Journal of the American College of Radiology. 2015;12(2):143–150. doi:10.1016/j.jacr.2014.09.038 Note: This tool applies to incidentally detected thyroid nodules only. Clinically palpable nodules or those detected during thyroid-specific workup follow different guidelines.
Incidental Liver Mass on CT
ACR White Paper — Gore, Pickhardt, Mortele et al.
Step 1 — Lesion Size (largest dimension)
< 1 cm
1.0 – 1.5 cm
> 1.5 cm
Step 2 — Patient Risk Profile
Low-risk patient
High-risk patient
Low-risk: No known malignancy, no hepatic dysfunction, no hepatic risk factors High-risk: Known malignancy with hepatic metastasis propensity, cirrhosis, or hepatic risk factors
Reference: Gore RM, Pickhardt PJ, Mortele KJ, et al. Management of Incidental Liver Lesions on CT: A White Paper of the ACR Incidental Findings Committee.
Journal of the American College of Radiology. 2017;14(11):1429–1437. Note: This algorithm applies to incidental liver masses detected on CT in patients without known liver disease or prior liver imaging. For known hepatocellular carcinoma or metastatic disease workup, use LI-RADS criteria.
Incidental Pancreatic Cyst
ACR White Paper — Megibow, Baker, Morgan et al., JACR 2017
Step 1 — Patient Age at Presentation
Age < 65 years
Age 65–79 years
Age ≥ 80 years
Step 2 — Cyst Size (longest dimension)
< 1.5 cm
1.5 – 2.5 cm
> 2.5 cm
Step 3 — MPD Communication
MPD communication established by imaging
MPD communication absent or cannot be determined
Step 3 — Imaging Features
SCA (serous cystadenoma features)
Low-risk by imaging
High-risk by imaging
EUS/FNA indicated at detection
Low-risk: No mural nodule, no wall thickening, normal caliber MPD, no peripheral Ca²⁺ High-risk: Mural nodules, wall thickening, MPD ≥7mm, peripheral Ca²⁺ High-risk stigmata: Extrahepatic biliary obstruction/jaundice, enhancing mural nodule, MPD ≥10mm → immediate EUS/FNA + surgical evaluation
Reference: Megibow AJ, Baker ME, Morgan DE, et al. Management of Incidental Pancreatic Cysts: A White Paper of the ACR Incidental Findings Committee.
Journal of the American College of Radiology. 2017;14(7):911–923. Growth definition: 100% increase in longest axis diameter for cysts <5mm; 50% increase for cysts ≥5mm and <15mm; 20% increase for cysts ≥15mm. Note: Imaging follow-up with contrast-enhanced MRI or pancreas protocol CT. EUS/FNA can be performed instead of imaging follow-up for larger or faster-growing cysts.
Incidental Renal Mass
ACR White Paper — Herts, Silverman, Hindman et al., JACR 2018
Step 1 — Does the Mass Contain Fat? (region < −10 HU)
No fat (does not contain region < −10 HU)
Contains fat (region measuring < −10 HU)
Step 2 — Imaging Available
Non-contrast CT only (unenhanced)
Contrast-enhanced CT only
Completely characterized (CT or MRI with & without IV contrast)
Step 3 — Morphology on Non-contrast CT
TSTC (too small to characterize), homogeneous
Homogeneous, thin/imperceptible wall, no nodule/septa/calcification
Heterogeneous, thick/irregular wall, mural nodule, septa or calcification
Step 4 — Attenuation (HU)
−10 to 20 HU
21 to 69 HU
≥ 70 HU
Step 4 — TSTC Assessment
Likely benign cyst (subjectively)
Inconclusive based on subjective evaluation
Step 3 — Morphology on Contrast-enhanced CT
TSTC (too small to characterize), homogeneous
Homogeneous, thin/imperceptible wall, no nodule/septa/calcification
Heterogeneous, thick/irregular wall, mural nodule, septa or calcification
Step 4 — Attenuation (HU)
−10 to 20 HU (benign cyst)
> 20 HU (solid or complicated cystic mass)
Step 4 — TSTC Assessment
Likely benign cyst
Inconclusive based on subjective evaluation
Step 3 — Mass Type
Cystic mass
Solid mass or TSTC
Step 4 — Bosniak Classification
Bosniak I or II
Bosniak IIF
Bosniak III or IV
Step 4 — Solid Mass Size
TSTC (too small to characterize)
Solid mass < 1.0 cm
Solid mass 1.0 – 4.0 cm
Solid mass > 4.0 cm
Step 2 — Calcification Present?
No calcification — Angiomyolipoma (AML)
With calcification — Suspected RCC
Step 3 — AML Characteristics
Solitary, no documented growth
Multiple or growth on prior studies
Step 4 — AML Size
Size < 4 cm
Size ≥ 4 cm (AML with potential for clinical symptoms)
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Reference: Herts BR, Silverman SG, Hindman NM, et al. Management of the Incidental Renal Mass on CT: A White Paper of the ACR Incidental Findings Committee.
Journal of the American College of Radiology. 2018;15(2):264–273. TSTC: Too Small To Characterize — mass too small for reliable characterization but detected incidentally. WO&W: Without and with IV contrast (MRI preferred over CT for further characterization). Bosniak classification applies to completely characterized cystic masses only.
Incidental Pineal Cyst
ACR White Paper — Moonis, Mohan, Dubey et al., JACR 2025
Step 1 — Imaging Modality
MRI of the Brain
CT of the Head
Step 2 — Mass Effect or Signal/Attenuation Change?
Yes — Mass effect on aqueduct OR signal/attenuation change in tectum
No mass effect, no signal/attenuation change in tectum
Mass effect: Narrowing or compromised aqueduct with or without obstructive hydrocephalus MRI: Signal change in tectum | CT: Hypoattenuation in tectum
Step 3 — Cyst Type
Simple pineal cyst
Non-simple pineal cyst
Simple: Uniform T2 hyperintensity, thin wall, no internal complexity, no solid component Non-simple: Internal complexity, nodularity, thick walls, or solid enhancing component
Step 4 — Cyst Diameter
< 15 mm diameter
≥ 15 mm diameter
Step 4 — Cyst Diameter
< 10 mm diameter
≥ 10 mm diameter
📋 CT finding: Follow-up MRI of the Brain at 6 months recommended. Then follow management per MRI algorithm (Figure 1).
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Reference: Moonis G, Mohan S, Dubey P, et al. Management of Incidentally Discovered Pineal Cyst on CT and MRI: Recommendations from the ACR Incidental Findings Committee.
Journal of the American College of Radiology. 2025;23:117–122. Simple pineal cyst (MRI): Uniform T2 hyperintensity, no internal complexity, thin imperceptible wall, no solid enhancing component. Non-simple pineal cyst: Internal complexity, nodularity, thick wall, or solid/enhancing component — requires closer surveillance. Note: Mass effect on aqueduct or signal change in tectum → neurosurgical consultation regardless of cyst size or type.
Incidental Adrenal Mass (≥1 cm)
ACR White Paper — Mayo-Smith, Song, Boland et al., JACR 2017
Step 1 — Initial Imaging Features
Diagnostic benign imaging features
Indeterminate imaging features
Diagnostic benign: Myelolipoma, no enhancement, Ca²⁺ (calcification), ≤10 HU on NCCT, or signal drop on chemical shift MRI (benign adenoma) Indeterminate: Does not meet above benign criteria
Step 2 — Lesion Size
≥1 cm and <4 cm
≥4 cm
Step 3 — Cancer History
No cancer history
+ Cancer history
Step 3 — Prior Imaging Available?
Prior imaging available
No prior imaging — No cancer history
No prior imaging — + Cancer history & isolated adrenal mass
Reference: Mayo-Smith WW, Song JH, Boland GL, et al. Management of Incidental Adrenal Masses: A White Paper of the ACR Incidental Findings Committee.
Journal of the American College of Radiology. 2017;14(8):1038–1044. Note: This algorithm applies to incidental asymptomatic adrenal masses ≥1 cm detected on CT or MRI. Biochemical workup for hormonal activity (cortisol, aldosterone, catecholamines) should be performed in all cases regardless of imaging appearance.