Source: https://publish.smartsheet.com/42d18e874a164318a0f702481f2fbb70
ACR Whitepaper guidelines are evidence-based recommendations published by the ACR Incidental Findings committees to guide the follow-up management of incidentally identified lesions in all major organ systems.
Thyroid
Source: J.K. Hoang et al. Management of Incidental Thyroid Nodules Detected on Imaging: A White Paper of the ACR Incidental Findings Committee, JACR 2015
1 Fig 1. Flowchart for incidental thyroid nodules (ITNs) detected on CT or MRI. 1 The recommendations are offered as general guidance and do not apply to all patients, such as those with clinical risk factors for thyroid cancer. 2 Suspicious CT/MRI features include: abnormal lymph nodes and/or invasion of local tissues by the thyroid nodule. Abnormal lymph node features include: calcifications, cystic components, and/or increased enhancement. Nodal enlargement is less specific for thyroid cancer metastases, but further evaluation could be considered if an ITN has ipsilateral nodes >1.5 cm in short axis for jugulodigastric lymph nodes, and >1 cm for other lymph nodes. 3 Limited life expectancy and comorbidities that increase the risk of treatment or are more likely to cause morbidity and mortality than the thyroid cancer itself, given the nodule size; see text for details. Patients with comorbidities or limited life expectancy should not have further evaluation of the ITN, unless it is warranted clinically, or specifically requested by the patient or referring physician. 4 Further management of the ITN after thyroid ultrasound, including fineneedle aspiration, should be based on ultrasound findings.
2 Fig 2. Flowchart for incidental thyroid nodules (ITNs) detected on 18FDG-PET and other nuclear medicine studies. 1 The recommendations are offered as general guidance and do not apply to all patients, such as those with clinical risk factors for thyroid cancer. 2 Focal uptake may include one or more sites. Diffuse uptake in the thyroid without a corresponding mass is not considered to be focal. 3 Limited life expectancy and comorbidities that increase the risk of treatment or are more likely to cause morbidity and mortality than the thyroid cancer itself, given the nodule size; see text for details. Patients with comorbidities or limited life expectancy should not have further evaluation of the ITN, unless it is warranted clinically, or specifically requested by the patient or referring physician. 4 Further management of the ITN after thyroid ultrasound should include fine-needle aspiration for PET-avid ITN regardless of the ultrasound findings; see text for details. Avid nodules on other nuclear medicine scans can have ultrasound with the decision to perform FNA based on findings seen on the dedicated thyroid ultrasound.
3 Fig 3. Flowchart for incidental thyroid nodules (ITNs) detected on ultrasound for extrathyroidal structures. 1 The recommendations are offered as general guidance and do not apply to all patients, such as those with clinical risk factors for thyroid cancer. 2 Suspicious ultrasound features include microcalcifications, marked hypoechogenicity, lobulated or irregular margins, and tallerthan-wide shape on transverse view. In most cases, suspicious features may not be completely evaluated. 3 Limited life expectancy and comorbidities that increase the risk of treatment or are more likely to cause morbidity and mortality than the thyroid cancer itself, given the nodule size; see text for details. Patients with comorbidities or limited life expectancy should not have further evaluation of the ITN, unless it is warranted clinically, or specifically requested by the patient or referring physician. 4 Further management of the ITN, including fine-needle aspiration, should be based on the findings seen on the dedicated thyroid ultrasound.
Liver
Source: R.M. Gore et al. Management of Incidental Liver Lesions on CT: A White Paper of the ACR Incidental Findings Committee, JACR 2017.
4 Fig 1. Algorithm for incidental liver lesions. 1 If inadequate imaging is available to ascertain the presence of benign versus suspicious features in a 1-cm lesion, prompt MRI is advised. 2 Low-risk patient: no known primary malignancy, hepatic dysfunction, or hepatic risk factors (see Table 1). 3 High-risk patient: known primary malignancy with a propensity to metastasize to the liver, cirrhosis, and/or other hepatic risk factors (see Table 1). 4 Follow-up MRI in 3 to 6 months. May need more immediate follow-up in some scenarios. CT is also acceptable in a patient with cancer who is due for routine CT surveillance. 5 Benign features: sharp margin, homogeneous low attenuation (20 Hounsfield units [HU]) on noncontrast and/or portal venous–phase imaging, and characteristic features of hemangiomas, focal nodular hyperplasia (FNH), focal fatty sparing or deposition, or perfusional changes (see “Commonly Encountered Benign Lesions” subsection). If pseudo enhancement is present, a benign cyst may measure >20 HU; radiologists’ discretion is necessary. 6 Suspicious features: ill-defined margins, heterogeneous density, mural thickening or nodularity, thick septa, and intermediate to high attenuation on portal venous–phase imaging (>20 HU, in the absence of pseudo enhancement). If pre- and postcontrast CT is available, enhancement >20 HU is a suspicious feature. To evaluate, prefer MRI. 7 “Flash-filling” feature: uniform hyperenhancement relative to hepatic parenchyma on arterial-phase (including late arterial/early portal venous–phase) postcontrast imaging. If additional postcontrast phases are available to characterize lesion as benign (eg, hemangioma) or suspicious (eg, hepatocellular carcinoma), the lesion should be placed in one of those respective categories and not here. 8 Incidental hepatic lesions that are >1.5 cm and do not have benign features should at least undergo prompt MRI. Direct biopsy (without MRI) may be appropriate in some scenarios. Differentiation of FNH from adenoma is important, especially if larger than 3 cm and subcapsular in location; for such patients, MRI with gadoxetate disodium is advised. 9 If biopsy is pursued, core biopsy is preferred over fine-needle aspiration.
Pancreas
Source: A.J. Megibow et al. Management of Incidental Pancreatic Cysts: White Paper of the ACR Incidental Findings Committee, JACR 2017.
5 Fig 1. Size < 1.5 cm incidental pancreatic cyst. EUS: endoscopic ultrasound; FNA: fine needle aspiration; MPD: main pancreatic duct.
6 Fig 2A. Size 1.5-2.5 cm incidental pancreatic cyst, with MPD communication present by imaging. cPNET: cystic pancreatic neuroendocrine tumor; EUS: endoscopic ultrasound; FNA: fine needle aspiration; SCA: serous cystadenoma.
7 Fig 2B. Size 1.5-2.5 cm incidental pancreatic cyst, with MPD communication absent or cannot be determined by imaging.
8 Fig 3. Size > 2.5 cm incidental pancreatic cyst. EUS: endoscopic ultrasound; FNA: fine needle aspiration; SCA: serous cystadenoma.
9 Fig 4. Incidental pancreatic cyst in patients age older than 80. EUS: endoscopic ultrasound; FNA: fine needle aspiration; SCA: serous cystadenoma.
Adrenals
Source: W.W. Mayo-Smith et al. Management of the Incidental Adrenal Masses: White Paper of the ACR Incidental Findings Committee, JACR 2017.
Fig 1. Algorithm for evaluation of an incidentally detected adrenal mass. (1) Consider biochemical assays to determine functional status and exclude pheochromocytoma before biopsy/resection. (2) “No enhancement” applies if an examination without and with intravenous contrast is available. (3) “Isolated” defined as no other metastatic disease identified. (4) May consider chemical shift MRI (CS-MR). APW: absolute percentage washout; RPW: relative percentage washout.
Kidneys
Source: B.R. Herts et al. Management of the Incidental Renal Mass on CT: White Paper of the ACR Incidental Findings Committee, JACR 2017.
11 Fig 1. Flowchart for managing an incidental renal mass on noncontrast CT. 1 If the mass contains fat attenuation (a region of interest < -10 HU), refer to Figure 5. 2 Too small to characterize. 3 Well-circumscribed and homogeneous TSTC renal masses that are visually much lower or much higher than the unenhanced renal parenchyma are probably benign cystic lesions. 4 MRI is preferred for characterizing smaller masses (<1.5 cm) and for detecting enhancement in suspected hypovascular masses. Ultrasound may be able to characterize a homogeneous hyperattenuating renal mass as a hemorrhagic or proteinaceous cyst. 5 If old images are available, any renal mass that has been without change in imaging features and has had an average growth of 3 mm per year for at least 5 years is likely of no clinical significance and does not need further workup. TSTC: too small to characterize.
Fig 2. Flowchart for managing an incidental renal mass on contrast-enhanced CT. 1 If the mass contains fat attenuation (a region of interest < -10 HU), refer to Figure 5. 2 Too small to characterize. 3 Well-circumscribed and homogeneous TSTC renal masses that are visually much lower than the enhanced renal parenchyma are probably benign cystic lesions. 4 MRI is preferred for characterizing smaller masses (< 1.5 cm) and for detecting enhancement in suspected hypovascular masses. Ultrasound may be able to characterize a homogeneous renal mass as a hemorrhagic or proteinaceous cyst. 5 If old images are available, any renal mass that has been without change in imaging features and has had an average growth of 3 mm per year for at least 5 years is likely of no clinical significance and does not need further workup.
12 Fig 3. Flowchart for managing a cystic renal mass on CT or MRI performed both without and with IV contrast. 1 If the mass contains fat attenuation (a region of interest < -10 HU), refer to Figure 5. 2 Morphologic change includes increasing number of septa, thickening of the wall or septa, or development of a solid nodular component (including reclassification as Bosniak III or IV). Growth of a cystic mass without morphologic change is not indicative of malignancy. 3 A Bosniak IIF cystic renal mass without change in imaging features for at least 5 years is considered stable and likely of no clinical significance.
13 Fig 4. Flowchart for managing for a completely characterized solid renal mass or renal mass too small to characterize on CT or MRI performed both without and with IV contrast. 1 If the mass contains fat attenuation (a region of interest < 10 HU), refer to Figure 5. 2 Too small to characterize. 3 Size ¼ largest diameter in any plane, follows TNM version 7 staging criteria. 4 Well-circumscribed TSTC renal masses, either calcified or noncalcified but that are otherwise homogeneous and either visually much lower than the renal parenchyma on any phase or much higher than the unenhanced renal parenchyma, are probably benign cystic lesions that do not need further evaluation. 5 MRI is preferred for characterizing smaller renal masses (< 1.5 cm) and for detecting enhancement in suspected hypovascular masses. 6 A renal mass without change in imaging features and with an average growth of <=3 mm per year for at least 5 years is considered stable and likely of no clinical significance. 7 Growth is defined as >=4 mm per year average; morphologic change is any change in heterogeneity, such as a change in contour, attenuation, or number of septa. 8 Consider biopsy, especially if hyperattenuating on unenhanced CT, or hypointense on T2WI MRI, because these are suggestive of a fat-poor angiomyolipoma. 9 If a pathologic diagnosis is desired to determine management but biopsy is technically challenging, or there is another relative contraindication to biopsy, consider MRI to assess the signal intensity on T2WI. Fat-poor angiomyolipoma and papillary renal cell carcinoma may be hypointense on T2WI in contrast to clear cell renal cell carcinoma, which is typically heterogeneous and mildly hyperintense on T2WI.
14 Fig 5. Flowchart for managing an incidental renal mass with a region of interest measuring fat attenuation (less than -10 HU). 1 Incidental sporadic AML (ie, no hematuria, flank pain, or perilesional hemorrhage.) 2 Many urologists will follow patients with small AMLs that are rapidly growing and some patients with multiple AMLs may benefit from an evaluation for tuberous sclerosis complex. 3 If only an unenhanced CT has been performed, consider CT or MR without and with IV contrast. 4 Patients with symptomatic AMLs (hematuria, flank pain, spontaneous bleeding) should be referred to urology regardless of size. 5 AML >= 4 cm or those with aneurysms greater than 0.5 cm should be referred for prophylactic treatment. AML: angiomyolipoma.