Adnexal

Fig 1. Management of incidental adnexal masses detected on CT or MR. (ACR 2020)

aExclusions:

1. normal findings, including crenulated enhancing wall of corpus luteum, asymmetric ovary without mass, with normal shape;
2. calcifications without associated noncalcified mass;
3. previous characterization with ultrasound (US) or MRI; or
4. documented stability in size and appearance for 2 years.

bLimited assessment on CT or MR: As defined in the article, this means the cyst is consistent with a simple-appearing cyst, but characterization is limited by low signal-to-noise ratio, artifact, lack of contrast assessment, or incomplete anatomic coverage.

c US or MRI to characterize means that the study should be performed promptly for further evaluation, rather than in follow-up to assess temporal changes.

dFully characterized by MR: As defined in the article, this means the cyst has been characterized with (1) T2-weighted images; (2) pre- and postcontrast T1-weighted images; and (3) complete anatomic coverage in at least two imaging planes.

eAssumes mass has not already been fully characterized by MR. Yellow boxes indicate using or acquiring clinical data (eg, lesion size), green boxes describe recommendations for action (eg, follow-up imaging), and red boxes indicate that work-up or follow-up may be terminated (eg, if the finding is presumed to be benign).

Mediastinal

Flowchart for evaluation of an incidentally detected mediastinal lymph node. (1) Short axis measurement is the standard. May consider further action if numerous small lymph nodes are present. (2) Explainable disease such as emphysema, interstitial lung disease, sarcoidosis, cardiac disease. (3) For unexplained causes, consider lymphoma, undiagnosed metastatic disease, including testicular carcinoma in young male, and infection. (4) Clinical consultation with referring provider or specialist.

Flowchart for evaluation of an incidentally detected mediastinal mass. (1) Localization most important for the differential diagnosis. (2) Consider benign, but may require resection if large and causing symptoms. (3) Modality depends on suspected etiology or malignancy potential.

Algorithm for evaluation of an incidentally detected pericardial abnormality. (1) Considered benign, but may require resection if large and impacts cardiac function. (2) Explainable disease such as autoimmune disease, prior radiation therapy, prior infection, history of renal disease, medications. (3) For unexplained causes, consider pericarditis (acute/ constrictive and infec- tion), post-myocardial infarction, undiagnosed disease such as metabolic (hypothyroidism, uremic), autoimmune, sarcoidosis.

Pituitary

Flowchart for incidental pituitary lesions detected on CT or MRI. (ACR 2018)

Flowchart for incidental pituitary lesions detected on FDG PET, regardless of metabolic activity.

Pancreatic

Flowchart (Chart 1) specifying the management of incidental pancreatic cysts <1.5 cm. EUS 1⁄4 endoscopic ultrasound; FNA 1⁄4 fine needle aspiration; MPD 1⁄4 main pancreatic duct. (ACR 2017)

Flowchart (Chart 2) specifying the management of incidental pancreatic cysts 1.5-2.5 cm, when main pancreatic duct (MPD) communication can be established (A), and when MPD communication is absent or cannot be determined (B). cPNET 1⁄4 cystic pancreatic neuroendocrine tumor; EUS 1⁄4 endoscopic ultrasound; FNA 1⁄4 fine needle aspiration; SCA 1⁄4 serous cystadenoma.

Flowchart (Chart 2) specifying the management of incidental pancreatic cysts 1.5-2.5 cm, when main pancreatic duct (MPD) communication can be established (A), and when MPD communication is absent or cannot be determined (B). cPNET 1⁄4 cystic pancreatic neuroendocrine tumor; EUS 1⁄4 endoscopic ultrasound; FNA 1⁄4 fine needle aspiration; SCA 1⁄4 serous cystadenoma.

Adrenal

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 1⁄4 absolute percentage washout; Caþþ 1⁄4 calcification; F/U 1⁄4 follow-up; HU 1⁄4 Hounsfield units; Hx 1⁄4 history; NCCT 1⁄4 CT without intravenous contrast; RPW 1⁄4 relative percentage washout; þ 1⁄4 positive. (ACR 2017)

Renal

Flowchart for managing an incidental renal mass on noncontrast CT. If the mass contains fat attenuation (a region of 23 interest<10HU),refertoFigure5. Toosmalltocharacterize. Well-circumscribed and homogeneous TSTC renal masses that 4 are visually much lower or much higher than the unenhanced renal parenchyma are probably benign cystic lesions.

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. 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. HU 1⁄4 Hounsfield unit; TSTC 1⁄4 too small to characterize; WO&W 1⁄4 without and with; W/ U 1⁄4 work-up. (ACR 2018)

Flowchart for managing an incidental renal mass on contrast-enhanced CT. If the mass contains fat attenuation (a region 23 of interest<10HU),refertoFigure5. Toosmalltocharacterize. Well-circumscribed and homogeneous TSTC renal masses 5 4 characterizing smaller masses (<1.5 cm) and for detecting enhancement in suspected hypovascular masses. Ultrasound may be that are visually much lower than the enhanced renal parenchyma are probably benign cystic lesions.

MRI is preferred for able to characterize a homogeneous renal mass as a hemorrhagic or proteinaceous cyst. mass that has been without change in imaging features and has had an average growth of likely of no clinical significance and does not need further workup. HU 1⁄4 Hounsfield unit; TSTC 1⁄4 too small to characterize; WO&W 1⁄4 without and with; W/U 1⁄4 work-up.

Flowchart for managing a cystic renal mass on CT or MRI performed both without and with IV contrast. If the mass 2 septa, thickening of the wall or septa, or development of a solid nodular component (including reclassification as Bosniak III or 3 contains fat attenuation (a region of interest < 10 HU), refer to Figure 5.

Morphologic change includes increasing number of IV). Growth of a cystic mass without morphologic change is not indicative of malignancy. without change in imaging features for at least 5 years is considered stable and likely of no clinical significance. HU 1⁄4 Hounsfield unit; IV 1⁄4 intravenous; WO&W 1⁄4 without and with; W/U 1⁄4 work-up.

Flowchart for managing for a completely characterized solid renal mass or renal mass too small to characterize on CT or 1 MRI performed both without and with IV contrast. If the mass contains fat attenuation (a region of interest

• 10 HU), refer 23 to Figure 5. Too small to characterize. Size 1⁄4 largest diameter in any plane, follows TNM version 7 staging criteria. 4Well-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 5 benign cystic lesions that do not need further evaluation. MRI is preferred for characterizing smaller renal masses(<1.5cm)and 6 average growth of 3 mm per year for at least 5 years is considered stable and likely of no clinical significance. Growth is for detecting enhancement in suspected hypovascular masses. defined as !4 mm per year average; morphologic change is any change in heterogeneity, such as a change in contour, 8 attenuation, or number of septa. MRI, because these are suggestive of a fat-poor angiomyolipoma. 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. HU 1⁄4 Hounsfield unit;

IV 1⁄4 intravenous; T2WI 1⁄4 T2-weighted imaging; WO&W 1⁄4 without and with; W/U 1⁄4 work-up.

Flowchart for managing an incidental renal mass with a region of interest measuring fat attenuation (less than 10 HU).

1Incidental sporadic AML (ie, no hematuria, flank pain, or perilesional hemorrhage.) 2Many urologists will follow patients with small AMLs that are rapidly growing and some patients with multiple AMLs may benefit from an evaluation for tuberous 34 sclerosis complex. If only an unenhanced CT has been performed, consider CT or MR without and with IV contrast. Patients 5 with symptomatic AMLs (hematuria, flank pain, spontaneous bleeding) should be referred to urology regardless of size. AML! 4 cm or those with aneurysms greater than 0.5 cm should be referred for prophylactic treatment. AML 1⁄4 angiomyolipoma; HU 1⁄4 Hounsfield unit; IV 1⁄4 intravenous; WO&W 1⁄4 without and with; W/U 1⁄4 work-up.

Liver

Algorithm for incidental liver lesions. If inadequate imaging is available to ascertain the presence of benign versus suspicious 2 features in a!1-cmlesion, prompt MRI is advised. Low-riskpatient: no known primary malignancy, hepatic dysfunction, or hepatic 3 risk factors(see Table1). High-risk patient: known primary malignancy with a propensity to metastasize to the liver, cirrhosis, and/or 4 other hepatic risk factors(seeTable1). Follow-up MRI in 3 to 6 months. May need more immediate follow-up in somescenarios.CT 5 is also acceptable in a patient with cancer who is due for routine CT surveillance. Benignfeatures: 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 pseudoenhancement is present, a benign cyst may measure >20 HU; radiologists’ 6 discretion is necessary. 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 7 post contrast CT is available, enhancement > 20 HU is a suspicious feature. To evaluate, prefer MRI. “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, he- 8 patocellular carcinoma), the lesion should be placed in one of those respective categories and not here. 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 9 such patients, MRI with gadoxetate disodium is advised. If biopsy is pursued, core biopsy is preferred over fine-needle aspiration.