Figure 1. Liver cyst. A 46-year-old woman with chronic abdominal pain underwent imaging. Ultrasonography of the right upper quadrant revealed a sharply marginated, anechoic lesion within the right lobe of the liver (asterisk) that demonstrates increased through transmission (arrows) (A) . A computed tomography scan with intravenous contrast agent was subsequently performed (B) . It also demonstrates a sharply marginated, fluid attenuation lesion within the right hepatic lobe (arrow).

Figure 2. Liver cyst. A 38-year-old woman with right upper quadrant pain underwent magnetic resonance cholangiopancreatography for suspected choledocholithiasis. A hypointense nonenhancing lesion with sharp margins is noted within the lateral segment of the left hepatic lobe (asterisk) on this axial T1-weighted magnetic resonance image after administration of gadolinium (A) . A uniformly hyperintense lesion is noted within the lateral segment of the left hepatic lobe (asterisk) on this axial T2-weighted magnetic resonance image (B) .

Figure 3. Hemangioma. A 32-year-old woman underwent ultrasonography of the right upper quadrant for abdominal pain. Imaging revealed a sharply marginated, uniformly hyperechoic mass within the right hepatic lobe (asterisk) that is most compatible with a diagnosis of benign hemangioma.

Figure 4. Hemangiomas. A 27-year-old woman with stage I cervical cancer underwent magnetic resonance imaging for suspicious liver lesions reported on ultrasonography (not available). Precontrast axial T1-weighted images demonstrate two hypointense lesions (arrows) within the right hepatic lobe (A) . After the administration of intravenous gadolinium, nodular, peripheral enhancement of these lesions (arrows) is visible in the arterial phase (B) with homogeneous enhancement (arrows) on delayed phase images (C) .

Figure 5. Focal nodular hyperplasia. A 44-year-old woman undergoes imaging for chronic left lower quadrant abdominal pain. Dual-phase computed tomography shows homogeneous arterial enhancement of a mass (arrow) within the right hepatic lobe with a characteristic hypodense central scar (A) . The mass (arrow) is relatively isodense to the background liver parenchyma on delayed images (B) .

Figure 6. Hepatic adenoma. A 37-year-old woman with a history of oral contraceptive use presented to the emergency department with acute right lower quadrant pain. Computed tomography was performed (not shown) that revealed a subtle mass in the right hepatic lobe. Subsequently, a magnetic resonance image was obtained that revealed a mass (arrow) in the right hepatic lobe that was relatively isointense to the background liver parenchyma ( A) . The mass (arrow) demonstrated avid, homogeneous enhancement in the arterial phase after the administration of intravenous gadolinium (B) that was slightly hypointense (arrow) on delayed images (C) .

Figure 7. Hepatic metastases. A 55-year-old woman with metastatic breast cancer underwent staging computed tomography of the abdomen that revealed two poorly marginated, mildly heterogeneous masses (asterisk) within the left hepatic lobe. Hepatic metastases were later confirmed by ultrasound-guided biopsy.

Figure 8. Cystic liver metastases from ovarian cancer. A 47-year-old woman with a large, palpable abdominal mass underwent computed tomography that revealed a massive cystic mass in the pelvis (asterisk), compatible with a diagnosis of an ovarian epithelial neoplasm. A mildly heterogeneous, low attenuation mass was likewise noted within the left hepatic lobe (arrow) that was compatible with a diagnosis of capsular metastases.

Figure 9. A workup algorithm for incidental liver mass detected on computed tomography. Abbreviations: CT indicates computed tomography; MRI, magnetic resonance imaging. Cross-references within the original figure legend are not active. (Reprinted from the Journal of American College of Radiology, Volume 14, Gore RM, Pickhardt PJ, Mortele KJ, Fishman EK, Horowitz JM, Fimmel CJ, et al. Management of incidental liver lesions on CT: a white paper of the ACR Incidental Findings Committee, pages 1429–37, Copyright 2017, with permission from Elsevier. https://www.sciencedirect.com/journal/journal-of-the-american-college-of-radiology .)

Figure 10.

Figure 11. A simple cyst on ultrasonography. A 37-year old woman with flank pain underwent routine retroperitoneal ultrasonography that revealed a sharply marginated, anechoic lesion (asterisk) arising from the right kidney (arrow). Color Doppler imaging demonstrated no internal or mural vascularity.

Figure 12. A simple cyst on magnetic resonance imaging. A 26-year-old woman with an incidentally detected renal mass on ultrasonography (not shown) underwent magnetic resonance imaging for further evaluation. A sharply marginated lesion was noted arising from the posterior aspect of the left kidney that was uniformly hypointense (arrow) on T1-weighted images (A) and uniformly hyperintense (arrow) on T2-weighted images (B) .

Figure 13. A Bosniak I renal cyst. A 44-year-old woman underwent routine computed tomography for evaluation of left lower quadrant pain. A sharply marginated, unilocular cyst (arrow) is noted arising from the posterior left kidney.

Figure 14. A Bosniak II renal cyst. A 47-year-old woman with chronic pelvic pain underwent computed tomography that showed a unilocular cyst arising from the lateral aspect of the left kidney that contained fine mural calcifications arising from the posterior wall of the cyst (arrow).

Figure 15. A Bosniak IIF renal cyst. A 38-year-old woman with chronic flank pain underwent routine computed tomography of the abdomen that revealed a mildly multilobular cyst arising from the anterior aspect of the right kidney (arrow). Fine, partially calcified septations are noted within the central aspect of the cyst. A simple cyst (asterisk) is noted arising from the left kidney.

Figure 16. A Bosniak III renal cyst. A 50-year-old woman with a ventral abdominal wall hernia underwent routine computed tomography of the abdomen that revealed an exophytic cyst arising from the upper pole of the right kidney containing mural calcifications and a thick, enhancing wall along the posterior margin of the cyst (arrow).

Figure 17. A Bosniak VI renal cyst. A 52-year-old woman with hematuria and right flank pain underwent computed tomography that showed a complex solid and cystic mass (arrows) arising from the mid-right kidney that is most compatible with a diagnosis of cystic renal neoplasm.

Figure 18. Angiomyolipomas. A 27-year-old woman underwent noncontrast computed tomography for suspected nephrolithiasis that revealed a uniformly hypodense, fat attenuation mass (isodense to the adjacent perinephric fat) arising from the posterior aspect of the left kidney (arrow) consistent with a diagnosis of angiomyolipoma (A) . A 33-year-old woman with suspected pancreatitis underwent imaging, which revealed a heterogeneous mass arising from the posterior margin of the right kidney containing small foci of macroscopic fat (arrow) that was likewise consistent with a minimal fat angiomyolipoma (B) .

Figure 19. Renal oncocytomas. A 57-year-old woman with suspected diverticulitis underwent routine computed tomography of the abdomen that revealed a sharply marginated, heterogeneously enhancing mass arising from the left kidney (arrow) that was consistent with a diagnosis of oncocytoma after left nephrectomy (A) . A 28-year-old woman with stage I melanoma underwent routine computed tomography of the abdomen that revealed a complex, low attenuation mass arising from the left kidney (arrow) containing scattered internal calcifications (B) . A partial nephrectomy was performed that was likewise consistent with oncocytoma. Both masses warrant surgical resection given that they are relatively indistinguishable from renal cell carcinoma on imaging.

Figure 20. Renal cell carcinoma (clear cell). A 55-year-old woman underwent routine computed tomography for the evaluation of hematuria and left flank pain. A large, exophytic mass (arrow) is noted arising from the posterior margin of the left kidney (A) on pre-contrast images that demonstrated avid, heterogeneous enhancement (arrow) after the administration of intravenous contrast agent (B) .

Figure 21. Workup algorithm for incidental cystic renal mass detected on computed tomography. Abbreviations: CT indicates computed tomography; IV, intravenous; MRI, magnetic resonance imaging; WO&W, without and with; W/U, workup. Cross-references within the original figure legend are not active. (Reprinted from the Journal of American College of Radiology, Volume 15, Herts BR, Silverman SG, Hindman NM, Uzzo RG, Hartman RP, Israel GM, et al. Management of the incidental renal mass on CT: a white paper of the ACR Incidental Findings Committee, pages 264–73, Copyright 2018, with permission from Elsevier. https://www.sciencedirect.com/journal/journal-of-the-american-college-of-radiology .)

Figure 22. Workup algorithm for incidental solid renal mass detected on computed tomography. Abbreviations: CT indicates computed tomography; MRI, magnetic resonance imaging. Cross-references within the original figure legend are not active. (Reprinted from the Journal of American College of Radiology, Volume 7, Berland LL, Silverman SG, Gore RM, Mayo-Smith WW, Megibow AJ, Yee J, et al. Managing incidental findings on abdominal CT: white paper of the ACR Incidental Findings Committee, pages 754–73, Copyright 2010, with permission from Elsevier. https://www.sciencedirect.com/journal/journal-of-the-american-college-of-radiology .)

Figure 23.

Figure 24. Von Hippel–Lindau syndrome. A 46-year-old woman with known von Hippel–Lindau syndrome underwent abdominal magnetic resonance imaging. Axial T2-weighted images revealed innumerable hyperintense cysts (arrow) of variable size throughout the pancreas.

Figure 25. Pancreatic pseudocyst. A 38-year-old woman with chronic ethyl alcohol abuse underwent routine computed tomography for the evaluation of pancreatitis. A sharply marginated cystic lesion is noted arising from the pancreatic head (arrow) that is most compatible with a pseudocyst.

Figure 26. Serous cystadenoma. A 68-year-old woman with left lower quadrant abdominal pain underwent computed tomography of the abdomen. Noncontrast images revealed a hypodense mass within the head of the pancreas (arrow) containing central calcifications (A) . There was no appreciable enhancement of the mass (arrow) with an intravenous contrast agent (B) . The discrete cystic elements typical of a serous cystadenoma were difficult to appreciate. However, a presumptive diagnosis of serous cystadenoma was established given the patient’s advanced age and lack of clinical symptoms.

Figure 27. Serous cystadenoma. A 72-year-old woman with suspected choledocholithiasis underwent abdominal magnetic resonance imaging. Axial T2-weighted images demonstrated a sharply marginated, multicystic mass (arrow) arising from the pancreatic head that is typical of a serous cystadenoma.

Figure 28. Mucinous cystadenomas. A 47-year-old woman underwent computed tomography for chronic abdominal pain. A sharply marginated, unilocular cystic lesion (arrow) was noted arising from the pancreatic tail (A) . The diagnosis of a mucinous cystadenoma was confirmed by endoscopic ultrasound-guided cyst aspiration. A 52-year-old woman with abdominal fullness underwent computed tomography that revealed a large, unilocular lesion with low attenuation arising from the body of the pancreas (arrow) that demonstrated subtle internal heterogeneity, consistent with proteinaceous debris (B) . The diagnosis of a mucinous cystadenomas was confirmed after surgical resection.

Figure 29. Side branch intraductal papillary mucinous tumor. A 48-year-old woman with right upper quadrant pain underwent abdominal magnetic resonance for suspected biliary colic. Coronal T2-weighted images demonstrated a multicystic mass within the uncinate process of the pancreas (arrow) that is most compatible with a side-branch intraductal papillary mucinous tumor, although a serous cystadenoma may present in a similar fashion. The diagnosis of intraductal papillary mucinous tumor was confirmed by the presence of excess mucin in the pancreatic duct on endoscopic retrograde cholangiopancreatography.

Figure 30. Main duct intraductal papillary mucinous tumor. A 55-year-old woman with epigastric abdominal pain underwent routine abdominal computed tomography that revealed marked dilatation along the entire course of the pancreatic duct (arrows), typical of a main duct intraductal papillary mucinous tumor. The diagnosis was confirmed by the presence of excess mucin in the pancreatic duct on endoscopic retrograde cholangiopancreatography.

Figure 31. Solid pseudopapillary neoplasms. A 33-year-old woman with nonalcoholic steatohepatitis underwent routine computed tomography that revealed a solid and cystic mass arising from the pancreatic body and tail (arrows). Although a pancreatic endocrine tumor may present in a similar fashion, a presumptive diagnosis of solid pseudopapillary epithelial neoplasm was established based on the patient’s relatively young age and lack of symptoms. The diagnosis was eventually established after distal pancreatectomy.

Figure 32. Pancreatic adenocarcinoma. A 62-year-old woman with jaundice and right upper quadrant pain underwent routine computed tomography that revealed a poorly marginated, ill-defined hypodense mass (arrow) within the proximal pancreatic body (A) . Extensive soft tissue encasement (arrows) of the celiac, common hepatic, and splenic arteries (B) was noted. These aggressive features are virtually pathognomonic for pancreatic adenocarcinoma.

Figure 33. Pancreatic metastases. A 53-year-old woman with a remote history of melanoma underwent surveillance computed tomography for abdominal pain. A poorly marginated hypodense mass was noted in the pancreatic neck (arrow). The diagnosis of pancreatic metastases from recurrent melanoma was ultimately established with endoscopic ultrasound-guided biopsy.

Figure 34. Workup algorithm for incidental cystic pancreatic mass detected on computed tomography. Abbreviations: BD-IPMN indicates branch duct intraductal papillary mucinous neoplasm; CT, computed tomography; MRCP, magnetic resonance cholangiopan-creatography; MRI, magnetic resonance imaging. (Reprinted from the Journal of American College of Radiology, Volume 7, Berland LL, Silverman SG, Gore RM, Mayo-Smith WW, Megibow AJ, Yee J, et al. Managing incidental findings on abdominal CT: white paper of the ACR Incidental Findings Committee, pages 754–73, Copyright 2010, with permission from Elsevier. https://www.sciencedirect.com/journal/journal-of-the-american-college-of-radiology .)

Figure 35.

Figure 36. Splenic hemangioma. A 43-year-old woman with lower abdominal pain underwent routine computed tomography demonstrating a hypoattenuating lesion (arrow) within the posterior spleen (A) . Magnetic resonance imaging was performed for further evaluation that revealed a well circumscribed T2 hyperintense mass (arrow) (B) with avid peripheral enhancement (arrow) in the arterial phase after the administration of intravenous gadolinium contrast (C) .

Figure 37. Splenic sarcoidosis. A 28-year-old woman with progressive dyspnea underwent computed tomography of the chest with findings of bilateral hilar adenopathy and multiple pulmonary nodules in a pattern consistent with sarcoidosis (not shown). Portions of the spleen were included that demonstrated numerous hypodense, nonenhancing lesions (arrow) of various sizes throughout the spleen.

Figure 38. Splenic metastases from ovarian carcinoma. A 62-year-old woman with abdominal fullness underwent computed tomography, which revealed a large ovarian mass (not shown) as well as an ill-defined hypodense liver lesion (left arrow) and hypodense splenic mass (right arrow) (A) . Positron emission tomography–computed tomography was performed for further workup of ovarian cancer demonstrating increased metabolic activity (arrow) within the splenic lesion (B) .

Figure 39.

Figure 40. Adrenal adenoma. A 43-year-old woman with flank pain underwent noncontrast computed tomography that revealed a homogenous, well-circumscribed left adrenal lesion (arrow) (A) . The Hounsfield measurement of the region of interest of the mass was −12 HU (circle), consistent with an adrenal adenoma (B) .

Figure 41. Nonspecific adrenal mass on adrenal washout computed tomography. A 52-year-old woman was found to have a heterogeneous left adrenal mass on a single-phase contrast enhanced computed tomography (CT) (not shown). Multiphase CT was subsequently performed according to an adrenal mass protocol. The mass was greater than 10 HU on noncontrast CT (A) with a calculated absolute washout of 46% using portal venous (B) and delayed imaging (C) . Therefore, this mass is not compatible with a benign adrenal adenoma, and additional workup, including history and laboratory evaluation, is required.

Figure 42. Adrenal adenoma on magnetic resonance imaging. A 56-year-old woman was found to have an incidental left adrenal mass on contrast-enhanced computed tomography (not shown). Magnetic resonance imaging was performed for further characterization. The mass is of intermediate signal intensity (arrow) on the in-phase T1-weighted images (A) and of lower signal intensity (arrow) on T1-weighted out-of-phase images (B). These findings are consistent with a lipid-rich adenoma.

Figure 43. Adrenal myelolipoma. A 68-year-old woman is evaluated for chronic abdominal pain. Axial (A) and coronal (B) images from contrast-enhanced computed tomography revealed a well-circumscribed heterogeneous right adrenal mass (arrows) with visible areas of fat attenuation.

Figure 44. Adrenal pheochromocytoma. A 46-year-old woman with episodic headaches, palpitations, and sweating undergoes imaging. Contrast-enhanced computed tomography demonstrates a large, heterogeneously enhancing mass (asterisk) within the right adrenal gland. Laboratory analysis yielded increased urine metanephrine levels, which helped to establish the diagnosis of pheochromocytoma.

Figure 45. Adrenal metastases. A 78-year-old woman with non-small-cell lung cancer underwent surveillance imaging. Bilateral, heterogeneously enhancing adrenal masses (arrows) are detected that were not present on previous images (not shown) and are compatible with metastases.

Figure 46. Adrenocortical carcinoma. A 47-year-old woman with abdominal pain and fullness underwent computed tomography. Imaging revealed a solid left adrenal mass (asterisk) with heterogeneous enhancement and central-low attenuation. The mass invades the left psoas muscle (arrow) with a loss of the normal intervening fat plane.

Figure 47. Workup algorithm for incidental adrenal mass detected on computed tomography or magnetic resonance imaging. Abbreviations: APW indicates absolute percentage washout; Bx, biopsy; Ca++, calcification; CT computed tomography; F/U, follow-up; HU, Hounsfield unit; CS-MR, chemical-shift magnetic resonance imaging; Hx, history; MRI, magnetic resonance imaging; NCCT, computed tomography without intravenous contrast; PET, positron emission tomography, RPW, relative percentage washout. (Reprinted from the Journal of American College of Radiology, Volume 14, Mayo-Smith WW, Song JH, Boland GL, Francis IR, Israel GM, Mazzaglia PJ, et al. Management of incidental adrenal masses: a white paper of the ACR Incidental Findings Committee, pages 1038–44, Copyright 2017, with permission from Elsevier. https://www.sciencedirect.com/journal/journal-of-the-american-college-of-radiology .)

Figure 48.

Figure 49. Nonspecific thyroid nodule. An 86-year-old woman with clinically palpable cervical lymphadenopathy underwent computed tomography of the neck that revealed a hypodense nodule (arrow) arising from the lower pole of the left thyroid lobe (A) . Thyroid ultrasonography was subsequently performed that revealed a mildly heterogeneous, predominantly solid nodule (arrows) (B) . Although the nodule warranted biopsy according to established criteria from the Society of Radiologists in Ultrasound, the patient elected to undergo imaging surveillance, particularly in light of her advanced age. Repeat ultrasonography demonstrated no change in the size or morphology of the nodule over several years.

Figure 50. Thyroid Imaging Reporting and Data System. (Data from ACR Thyroid Imaging, Reporting and Data System (TI-RADS): White Paper of the ACR TI-RADS Committee. Tessler, Franklin N. et al. Journal of the American College of Radiology, Volume 14, Issue 5, 587–95 .)

Figure 51. Spongiform thyroid nodule. A 44-year-old woman with a family history of thyroid cancer underwent routine thyroid ultrasonography, which revealed a sharply marginated nodule (arrows) with the midaspect of the left thyroid lobe. Multiple small cystic spaces are noted throughout the nodule, compatible with benign spongiform morphology.

Figure 52. Follicular adenoma. A 45-year-old woman underwent routine thyroid ultrasonography for a clinically palpable thyroid mass. A sharply marginated nodule was seen with the lower pole of the right thyroid lobe containing both solid (long arrow) and cystic (asterisk) elements. Doppler imaging demonstrated mild, nonspecific peripheral flow (short arrows) surrounding the nodule. Ultrasound-guided fine-needle aspiration revealed a follicular adenoma with cystic degeneration.

Figure 53. Colloid cyst. A 57-year-old woman underwent thyroid ultrasonography for a clinically palpable nodule. A sharply marginated cystic mass with avid through transmission was seen within the lower pole of the right thyroid lobe that corresponded to the clinically palpable nodule. Punctate echogenic foci were noted within the cyst (arrows) that are highly characteristic of a benign colloid cyst.

Figure 54. Papillary thyroid carcinoma. A 57-year-old woman with a family history of thyroid cancer underwent thyroid ultrasonography that revealed a heterogeneous, predominantly solid nodule within the upper pole of the left thyroid lobe. Multiple small calcifications (arrows) were scattered throughout the nodule that are highly concerning for malignancy. The nodule was assigned a TR5 score according to Thyroid Imaging Reporting and Data System criteria. A partial thyroidectomy was subsequently performed that confirmed the diagnosis of papillary thyroid carcinoma.

Figure 55. Multinodular goiter. A 58-year-old woman with a midline neck mass underwent thyroid ultrasonography that revealed diffuse, heterogeneous, nodular enlargement throughout both the right (R) and left (L) lobes (A) . Computed tomography of the thorax was subsequently performed in the same patient that demonstrated inferior extention of the goiter (arrows) into the anterior mediastinum (B).

Figure 56.

Figure 57. Histoplasmosis. A 55-year-old woman underwent CT of the thorax for nonspecific chest pain that revealed calcified nodules (arrows) throughout both lungs (A) . Multiple calcified hilar lymph nodes (arrows) also were noted (B) . These findings are typical of chronic histoplasmosis, a diagnosis that was clinically supported given that the patient permanently resided in the Ohio River Valley, where histoplasmosis infection reached endemic proportions.

Figure 58. Nonspecific subsolid nodule. A 44-year-old woman underwent computed tomography angiography of the thorax for suspected pulmonary embolism. A nonspecific ground glass or subsolid nodule (arrow) within the left upper lobe was noted incidentally. The nodule was presumably infectious in origin given its resolution on a 12-month follow-up study.

Figure 59. Pulmonary hamartoma. A 63-year-old woman with stage I endometrial carcinoma underwent routine staging computed tomography of the thorax that revealed a 2-cm heterogeneous nodule within the right lower pulmonary lobe. This finding is compatible with a benign pulmonary hamartoma given the presence of internal fat (arrow).

Figure 60. Adenocarcinoma of the lung. A 66-year-old woman with generalized malaise and weight loss underwent computed tomography of the thorax, which revealed a heterogeneous, spiculated mass (arrow) within the right upper pulmonary lobe that was highly concerning for a primary malignancy. Right upper lobectomy confirmed the diagnosis of adenocarcinoma of the lung.

Figure 61. Pulmonary metastases. A 56-year-old woman with a history of metastatic breast cancer underwent imaging. Coronal computed tomography demonstrates multiple noncalcified nodules of variable size throughout both lungs (arrows), consistent with widespread metastatic disease.

Figure 62. Workup algorithm for incidental solid pulmonary nodule detected on computed tomography. Abbreviations: CT indicates computed tomography; PET, positron emission tomography. (Data from MacMahon H, Naidich DP, Goo JM, Lee KS, Leung ANC, Mayo JR, et al. Guidelines for management of incidental pulmonary nodules detected on CT images: from the Fleischner Society 2017. Radiology 2017;284:228–43 .)

Figure 63. Workup algorithm for incidental subsolid pulmonary nodule detected on computed tomography. Abbreviation: CT indicates computed tomography. (Data from MacMahon H, Naidich DP, Goo JM, Lee KS, Leung ANC, Mayo JR, et al. Guidelines for management of incidental pulmonary nodules detected on CT images: from the Fleischner Society 2017. Radiology 2017;284:228–43 .)

Figure 64.

Table 1. Radiologic Terminology

Table 2. Hounsfield Unit Scale

Table 3. Bosniak Classification of Renal Cystic Masses