FDG PET/CT in the liver: lesions mimicking malignancies

PET/MRI: pictorial review of hepatobiliary and pancreatic applications

PET and MRI both play valuable roles in the management of hepatobiliary and pancreatic (HBP) malignancies. Simultaneous PET/MRI combines the excellent soft-tissue resolution and anatomic details from MRI with functional information from PET in a single comprehensive examination. MRI is the main imaging modality in evaluating HCC, playing important roles in screening, characterization, local extent, and evaluating tumor response, whereas 18F-fluorodeoxyglucose (FDG) PET can help evaluate for lymph node involvement and metastatic disease. In cholangiocarcinoma and pancreatic malignancies, both PET and MRI have excellent utility in initial staging as well as assessing treatment response. In all HBP malignancies, FDG-PET/MRI is a unique problem-solving tool in complex cases and diagnostic challenges, especially after locoregional therapy and when differentiating residual or recurrent viable disease from inflammatory and other benign processes. In this manuscript, we review the role of PET/MRI in the diagnosis, staging, assessing treatment response, and characterizing post-treatment processes. With the introduction of multiple new tracers, the value of PET/MRI has not yet been fully realized, and more studies are needed to demonstrate the utility and efficacy of PET/MRI in improving patient care in hepatobiliary and pancreatic oncology.

Detection of Rare Gallbladder Microperforation by 18F-FDG PET/CT in a Patient with Maxillary Sinus Cancer

Gallbladder perforation is one of the most serious complications of cholecystitis and is rarely seen in 2-11% of cases. Pericholecystic abscesses secondary to gallbladder perforation are rare. Rapid diagnosis is important because of high morbidity and mortalityrates. A subcapsular abscess secondary to gallbladder microperforation is presented on 18F-fluorodeoxyglucose positron emission tomography/computed tomography performed for restaging in a patient with maxillary sinus cancer.

Hepatic Cavernous Hemangioma Mimicking Malignancy on 18 F-FDG PET/CT Imaging

ABSTRACT

A 65-year-old woman was referred to our hospital because of a liver lesion revealed by ultrasound and CT in an outside institution. 18 F-FDG PET/CT images revealed an FDG-avid lesion in the left lateral lobe of the liver. Malignancy cannot be excluded. A subsequent resection was performed to remove the lesion. Postoperative pathology was hepatic cavernous hemangioma. This case suggests that PET/CT findings of FDG-avid hepatic cavernous hemangioma could mimic malignancy.

Hepato-Biliary Imaging in an Acute Setting: Is There a Role for Nuclear Medicine?

Nuclear medicine (NM) is not commonly considered as a first-line imaging modality in hepato-biliary (HB) emergencies. The aim of this review is to provide an update on the potential of NM for the imaging of HB emergencies. 99mTc-HIDA scintigraphy showed high diagnostic accuracy for acute cholecystitis, thus being particularly useful in patients at high-risk for surgery due to comorbidities and with no clear findings at US or CT. Although limitedly explored, White blood cell (WBC) scan might have a role in case of acute pancreatitis, especially for the imaging of pancreatic leukocyte infiltration and the prediction of pancreatic necrosis. Scientific literature on 18F-FDG-PET/CT in HB acute disease mainly consists of case reports or case series, describing incidental findings in oncological PET/CT scans. In patients with obstructive jaundice, PET/CT has been proposed to disclose and characterize occult tumoral etiology. Further studies are needed to evaluate the clinical usefulness of the various NM approaches in HB acute settings, particularly with respect to the emerging new technologies (eg, PET/MRI) and radiopharmaceuticals.

The Role of 68Ga FAPI-04 and 18F-FDG PET/CT in Detecting Liver Metastases in Different Types of Cancer

OBJECTIVE

We compared the diagnostic accuracies of 68Ga FAPI-04 PET/CT and 18F-FDG PET/CT for detecting liver metastases (LMs) in patients with different cancer types.

MATERIALS AND METHODS

This retrospective study included 63 patients with liver lesions who underwent 18F-FDG PET/CT and 68Ga-FAPI-04 PET/CT between May 2020 and May 2022. Patients with histopathologically confirmed primary diagnoses, data that could be accessed retrospectively, liver lesions confirmed by biopsy over at least 3-6 months of follow-up (via ultrasonography, CT, magnetic resonance imaging, PET/CT, or laboratory tests) were included. Patients with secondary malignancies or primary liver malignancies, and/or who could not be followed-up, were excluded.

RESULTS

Of the 63 total patients, 34 (54%) were female, and the mean age was 61 (30-92) years. There were 582 LMs in 51 patients and 35 benign liver lesions in 20 (12 patients had only benign and 8 both benign and malignant lesions). Of the 582 LMs, 472 (81.1%) evidenced 18F-FDG uptake and 572 (98.2%) 68Ga-FAPI uptake. The diagnostic accuracies of 68Ga-FAPI PET/CT and 18F-FDG PET/CT were 98% and 82%, respectively (p < 0.001; McNemar test). When the LMs were compared, the maximum standardized uptake (SUVmax) value was significantly higher on 18F-FDG PET/CT than 68Ga-FAPI PET/CT (median: 6.0 vs. 5.4; p = 0.016). However, the LM-to-background ratio (TBR) was significantly higher on 68Ga-FAPI PET/CT than 18F-FDG PET/CT (median: 4.1 vs. 2.1; p < 0.001).

CONCLUSION

68Ga-FAPI PET/CT detected more LMs than did 18F-FDG PET/CT, and TBR was significantly higher on 68Ga-FAPI PET/CT than 18F-FDG PET/CT.

Is Prone Position [18F]FDG PET/CT Useful in Reducing Respiratory Motion Artifacts in Evaluating Hepatic Lesions?

Prone position is useful in reducing respiratory motion artifacts in lung nodules on 2-Deoxy-2-[18F] fluoro-D-glucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT). However, whether prone position PET/CT is useful in evaluating hepatic lesions is unknown. Thirty-five hepatic lesions from 20 consecutive patients were evaluated. The maximum standardized uptake value (SUVmax) and metabolic tumor volume (MTV) of both standard supine position PET/CT and additional prone position PET/CT were evaluated. No significant difference in SUVmax (4.41 ± 2.0 vs. 4.23 ± 1.83; p = 0.240) and MTV (5.83 ± 6.69 vs. 5.95 ± 6.24; p = 0.672) was observed between supine position PET/CT and prone position PET/CT. However, SUVmax changes in prone position PET/CT varied compared with those in supine position PET/CT (median, -4%; range: -30-71%). Prone position PET/CT was helpful when [18F]FDG uptake of the hepatic lesions was located outside the liver on supine position PET/CT (n = 4, SUVmax change: median 15%; range: 7-71%) and there was more severe blurring on supine position PET/CT (n = 6, SUVmax change: median 11%; range: -3-32%). Unlike in lung nodules, prone position PET/CT is not always useful in evaluating hepatic lesions, but it may be helpful in individual cases such as hepatic dome lesions.

Findings of cholangitis in a kidney transplant patient with Caroli disease on FDG PET/CT and MRI

Caroli disease is a rare congenital disorder of segmental cystic dilatations of the intrahepatic biliary ducts that maintain communication with the rest of the biliary tree. Its typical clinical presentation is recurrent episodes of cholangitis. The diagnosis is usually made using abdominal imaging modalities. We present a patient with Caroli disease showing atypical presentation of acute cholangitis with ambiguous labs and initial negative imaging findings, which was later diagnosed by [18F]-fluorodeoxyglucose positron emission tomography/computed tomography and confirmed by magnetic resonance imaging and tissue pathology. The use of such imaging modalities in moments of doubt or clinical suspicion provide the patient with accurate diagnosis, proper management, and better clinical outcome, thus obviating the need for further invasive investigations.

Spilled gallstone mimicking metastasis from cervix cancer on positron emission tomography – computed tomography

BACKGROUND

Spilled gallstones from previous cholecystectomy is not an uncommon situation. It may further mimic neoplastic disease and can be misled by fluorine 18 fluorodeoxyglucose position emission tomography with computed tomography ([18F]FDG PET/CT).

CASE SUMMARY

A 63 year-old patient was diagnosed with a cancer of the cervix. Pretreatment [18F]FDG PET/CT showed a peritoneal lesion suspicious for metastasis. Surgical exploration and histologic examination revealed the lesion to be a spilled gallstone from a previous cholecystectomy.

CONCLUSION

[18F]FDG PET/CT carries pitfalls since benign conditions such as intraperitoneal gallstones may be confused as malignant lesions. This case highlights the importance to be aware of the possible implications of dropped gallstones for the future, minimize its occurrence, and make all efforts to properly evaluate cancer staging, particularly for the cervix cancer.

A Rare Case of Combined Langerhans Cell Histiocytosis and Adult-Onset Xanthogranuloma: A Case Report

Langerhans cell histiocytosis (LCH) and adult-onset xanthogranuloma (AXG) are rare disorders characterized by the accumulation of macrophage, dendritic cells, or monocyte-derived cells in various tissues of the body. Many researchers now consider LCH a form of malignancy, but this classification remains controversial. As per our knowledge, there are only 36 cases of AXG reported so far in the English literature. Here, we report a case of AXG and single-system LCH found in the oral cavity and cervical lymph nodes, respectively. In this article, we intend to define a clear understanding of some classic clinical, radiological, and histopathological findings of LCH and AXG, to differentiate them from oral malignancies. The primary goal of this article is to increase awareness regarding conditions that closely resemble malignancies and to save patients from the burden of extensive treatment under the presumption of malignant disorders. In the medical field, reporting of rare cases is highly encouraged; however, proper treatment for the patient depends on the accurate diagnosis that, in this case, was made postoperatively, which only added more physical and mental distress for the patient and their family.

FDG PET/CT for Primary Staging of Lung Cancer and Mesothelioma

Lung cancer is the leading cause of cancer-related mortality in the United States. Accurate staging at initial diagnosis determines appropriate treatment and is the most important predictor of survival. Since 2018, the 8th edition of the TNM staging system has been used to stage lung cancer based on local tumor extent (T), nodal involvement (N), and metastases (M). 18 F fluorodeoxyglucose (FDG) PET/CT, which combines functional and anatomic imaging, is the standard of care and an integral part of clinical staging of patients with lung cancer. Malignant pleural mesothelioma (MPM), the most common primary malignant pleural tumor affecting the pleura is staged with 8th edition of TNM staging for MPM. 18 F FDG PET/CT is indicated in select patients who are surgical candidates to identify locally advanced tumor, nodal metastases, or extrathoracic metastases, which may preclude surgery.

Steatotic Hepatitis Presenting as a Huge Hypermetabolic Liver Mass

ABSTRACT

FDG PET/CT scan is a diagnostic imaging modality for oncologic patients, but with false-positive findings in inflammatory diseases. In this interesting case, we present a 24-year-old woman with history of giant cell tumor of the bone (lumbar vertebrae) who underwent whole-body FDG PET/CT scan for treatment response evaluation. FDG PET/CT scan demonstrated a large hypermetabolic tumoral mass lesion in segment VI/VII of the right hepatic lobe. A range of malignant versus benign lesions should be considered as differential diagnoses, including metastasis, primary cholangiocarcinoma, hepatocellular carcinoma, focal nodular hyperplasia, and infection. Final diagnosis of "steatotic hepatitis" after CT-guided biopsy was established.

Differentiation of Small Hepatic Abscess From Hepatic Metastasis With a Combination of Imaging Parameters

OBJECTIVE

We aimed to evaluate the diagnostic performance of the combination imaging features to differentiate small (the lesion size of 3 cm or less) hepatic abscess from metastasis.

METHODS

This retrospective study included patients with preexisting malignancy and small hepatic lesions who underwent contrast-enhanced computed tomography (CT) and gadoxetic acid-enhanced magnetic resonance imaging (MRI) within 4 days between March 2017 and July 2020. Two radiologists independently evaluated the imaging features of each focal hepatic lesion. Laboratory parameters were also recorded. Significant parameters differentiating hepatic abscess from hepatic metastasis were identified by univariate generalized estimating equation regression. We compared the diagnostic performances of laboratory parameters, imaging features, and their combinations.

RESULTS

We included 16 patients (10 males and 6 females) with 35 hepatic abscesses and 21 patients (13 males and 8 females) with 62 metastases with a mean age of 70.3 years in this study. Abnormal segmental neutrophil, pathy parenchymal enhancement on CT, and absence of dark rim on MRI were associated with hepatic abscess (all P < 0.01). The combination of CT and MRI parameters showed significantly higher specificity and positive predictive value than CT alone (P ≤ 0.031), without significant difference in sensitivity and negative predictive value.

CONCLUSIONS

We have demonstrated that the combination of CT and MRI imaging features is helpful for the differentiation of small hepatic abscess from metastasis.

F-18 Fluoro-2-Deoxyglucose Positron Emission Tomography (PET)/Computed Tomography (CT) Imaging in Melanoma: Normal Variants, Pitfalls, and Artifacts

Multimodality imaging has revolutionized diagnostic imaging for several oncologic pathologies including melanoma. Although F-18 fluoro-2-deoxyglucose positron emission tomography/ computed tomography [18F]FDG PET/CT has a high sensitivity in stage III and IV melanoma, several normal variants, and imaging pitfalls may result in falsely increased or reduced tracer uptake that may negatively impact diagnostic accuracy. In addition to normal physiologic tracer uptake, differences in the biological and molecular characteristics of different types of melanoma are also responsible for pitfalls. For instance, [18F]FDG PET/CT has a low sensitivity for detecting brain metastases due to normal physiologic [18F]FDG uptake in brain tissue while hepatic metastases from cutaneous melanoma are more [18F]FDG-avid than hepatic metastases from uveal melanoma. With the introduction of immunotherapies for melanoma, treatment response assessment using [18F]FDG PET/CT has a reduced specificity. This is due to hypermetabolic immune-related adverse effects such as hepatitis, dermatitis, and colitis resulting in false-positive uptake. In addition, immune therapy-induced initial increase in tumor uptake followed by disease response (pseudo-progression) is a cause of false-positive scan interpretation. Specific technical artifacts impact disease detection in [18F]FDG PET/CT melanoma imaging. The identification of small metastatic lymph nodes and lung nodules may be limited by the resolution of the PET/CT camera (partial volume effect). Computed tomography (CT) attenuation correction results in less apparent skin and subcutaneous lesions. Pictorial illustrations will be central to this paper for the description of these normal variants, imaging artifacts, and pitfalls. It is critical for the imaging specialist to have a clear understanding of these potential limitations of 18F-FDG PET/CT imaging in individuals who are referred with melanoma.

Morphological, dynamic and functional characteristics of liver pseudolesions and benign lesions

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide and one of the most common causes of death among patients with cirrhosis, developing in 1-8% of them every year, regardless of their cirrhotic stage. The radiological features of HCC are almost always sufficient for reaching the diagnosis; thus, histological confirmation is rarely needed. However, the study of cirrhotic livers remains a challenge for radiologists due to the developing of fibrous and regenerative tissue that cause the distortion of normal liver parenchyma, changing the typical appearances of benign lesions and pseudolesions, which therefore may be misinterpreted as malignancies. In addition, a correct distinction between pseudolesions and malignancy is crucial to allow appropriate targeted therapy and avoid treatment delays.The present review encompasses technical pitfalls and describes focal benign lesions and pseudolesions that may be misinterpreted as HCC in cirrhotic livers, providing the imaging features of regenerative nodules, large regenerative nodules, siderotic nodules, hepatic hemangiomas (including rapidly filling and sclerosed hemangiomas), segmental hyperplasia, arterioportal shunts, focal confluent fibrosis and focal fatty changes. Lastly, the present review explores the most promising new imaging techniques that are emerging and that could help radiologists differentiate benign lesions and pseudolesions from overt HCC.

Multi-Modal Co-Learning for Liver Lesion Segmentation on PET-CT Images

Liver lesion segmentation is an essential process to assist doctors in hepatocellular carcinoma diagnosis and treatment planning. Multi-modal positron emission tomography and computed tomography (PET-CT) scans are widely utilized due to their complementary feature information for this purpose. However, current methods ignore the interaction of information across the two modalities during feature extraction, omit the co-learning of the feature maps of different resolutions, and do not ensure that shallow and deep features complement each others sufficiently. In this paper, our proposed model can achieve feature interaction across multi-modal channels by sharing the down-sampling blocks between two encoding branches to eliminate misleading features. Furthermore, we combine feature maps of different resolutions to derive spatially varying fusion maps and enhance the lesions information. In addition, we introduce a similarity loss function for consistency constraint in case that predictions of separated refactoring branches for the same regions vary a lot. We evaluate our model for liver tumor segmentation using a PET-CT scans dataset, compare our method with the baseline techniques for multi-modal (multi-branches, multi-channels and cascaded networks) and then demonstrate that our method has a significantly higher accuracy ( ) than the baseline models.

Evaluation of the Diagnostic Performance of Positron Emission Tomography/Magnetic Resonance for the Diagnosis of Liver Metastases

OBJECTIVE

The aim of this study was to compare the performance of positron emission tomography (PET)/magnetic resonance (MR) versus stand-alone PET and stand-alone magnetic resonance imaging (MRI) in the detection and characterization of suspected liver metastases.

MATERIALS AND METHODS

This multi-institutional retrospective performance study was approved by the institutional review boards and was Health Insurance Portability and Accountability Act compliant, with waiver of informed consent. Seventy-nine patients with confirmed solid extrahepatic malignancies who underwent upper abdominal PET/MR between February 2017 and June 2018 were included. Where focal hepatic lesions were identified, the likelihood of a diagnosis of a liver metastasis was defined on an ordinal scale for MRI, PET, and PET/MRI by 3 readers: 1 nuclear medicine physician and 2 radiologists. The number of lesions per patient, lesion size, and involved hepatic segments were recorded. Proof of metastases was based on histopathologic correlation or clinical/imaging follow-up. Diagnostic performance was assessed using sensitivity, specificity, positive and negative predictive values, and receiver operator characteristic curve analysis.

RESULTS

A total of 79 patients (53 years, interquartile range, 50-68; 43 men) were included. PET/MR had a sensitivity of 95%, specificity of 97%, positive predictive value of 97%, and negative predictive value of 95%. The sensitivity, specificity, positive predictive value, and negative predictive value of MRI were 88%, 98%, 98%, and 90% and for PET were 83%, 97%, 97%, and 86%, respectively. The areas under the curve for PET/MRI, MRI, and PET were 95%, 92%, and 92%, respectively.

CONCLUSIONS

Contrast-enhanced PET/MR has a higher sensitivity and negative predictive value than either PET or MRI alone in the setting of suspected liver metastases. Fewer lesions were characterized as indeterminate by PET/MR in comparison with PET and MRI. This superior performance could potentially impact treatment and management decisions for patients with suspected liver metastases.

Hepatic actinomycosis after total pancreatectomy: A case report

Introduction and importance

Hepatic actinomycosis (HA) is a rare infection mimicking a malignancy. HA after total pancreatectomy for a pancreatic tumor has not been reported.

Case presentation

A 70-year-old woman with a history of gastrectomy and sigmoidectomy for benign lesions, underwent a total pancreatectomy for a non-invasive, intraductal papillary mucinous carcinoma (IPMC). She required partial resection of the transverse colon due to insufficient blood flow and had an anastomotic failure. Four months later, she developed a fever and effusion from the upper abdominal midline incision. No bacteria were cultured from the effusion. Contrast-enhanced computed tomography demonstrated an 80-mm iso-vascular liver mass. A slightly high-signal intensity on T2-weighted magnetic resonance imaging was demonstrated. Positron emission tomography (PET) showed a standardized uptake value of 11.9 at the liver mass. The percutaneous liver biopsy did not establish a diagnosis. Because a malignancy could not be ruled out, an exploratory laparotomy was performed. A tissue sample revealed aggregates of branched filamentous microorganisms; actinomycosis was diagnosed. Oral amoxicillin for 4 months resolved the mass.

Clinical discussion

This patient had several causative factors for HA, including multiple surgical procedures involving the gastrointestinal tract, reconstruction of the biliary tract, anastomotic failure of the transverse colon, and diabetes mellitus following total pancreatectomy. Based on the past treatment history for IPMC and PET findings mimicking a malignancy, a laparotomy was performed to biopsy the lesion. Typically, penicillin is recommended for >6 months.

Conclusion

A rare case of HA mimicking a malignancy after a total pancreatectomy for IPMC is presented.

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Hepatic actinomycosis (HA) is a rare infection mimicking a malignancy.

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A total pancreatectomy and gastrointestinal surgeries were the causable factors.

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Typically, penicillin therapy is recommended for over 6 months.

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Surgical exploration was important avoiding unnecessary hepatectomy.

PET/CT Normal Variants and Pitfalls in Pediatric disorders

18F- Fluoro-deoxyglucose positron emission computed tomography (18F-FDG PET CT) is an established modality used mainly in oncology. Though it has widespread oncologic indications, it is not tumor specific. Apart from the physiological distribution, uptake of FDG may be seen in many benign conditions, including infection and inflammation in children and adults. Performing and acquiring a technically adequate PET CT study may be more challenging in children. Proper preparation and an acceptable imaging protocol will help to avoid re-acquisition and in minimizing the radiation exposure. Sound knowledge of the physiological variants and benign conditions that are specific to the pediatric population will aid in correct interpretation of the PET CT study. It is important that radiologists and Nuclear Medicine physicians who report these studies are well-acquainted with these pitfalls to avoid false positive studies.

Liver Abscess With High 18F-FDG Uptake and No 18F-Fluorothymidine Uptake

ABSTRACT

18F-FDG accumulates not only in malignant lesions but also in infectious and inflammatory ones. 3'-deoxy-3'-18F-fluorothymidine (FLT) has been investigated as a promising PET tracer for evaluating tumor proliferating activity. We report a case of liver abscess during therapy of pancreatic cancer that underwent FDG PET/CT and FLT PET/CT studies. Although FDG PET/CT demonstrated several regions of increased uptake in the liver, FLT PET/CT showed no increased uptake in the liver.

Value of 18F-FDG PET/CT in patients with hepatic metastatic carcinoma of unknown primary

PURPOSE

This retrospective study aimed to investigate the clinical value of -deoxy-2-(F)-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) in detecting primary lesions of hepatic metastases.

METHODS

A total of 124 patients with hepatic metastatic carcinoma of unknown primary underwent whole body F-FDG PET/CT imaging. According to the final diagnoses for both primary sites and hepatic metastases that were confirmed either histopathologically or by clinical follow up, all patients were divided into 4 groups: a true positive group (TP, 95 cases), a false positive group (FP, 9), a true negative group (TN, 8) and a false negative group (FN, 12).

RESULTS

The TP rate of primary lesions, detected by F-FDG PET/CT, was 76.61%, the FP rate 7.26%, the TN rate 6.45% and the FN rate 9.68%. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of F-FDG PET/CT in the detection of primary tumors were 88.78%, 52.94%, 91.35%, 40%, and 83.06%, respectively. Accurate diagnosis groups (TP, TN) showed a significantly higher SUVmax (standard uptake maximum value) level than that in error diagnosis groups (FP, FN). The SUVmax between hepatic metastases and primary lesions had a positive correlation. The primary tumor sites of hepatic metastases were mainly located in the gastrointestinal organs and the lungs.

CONCLUSIONS

Whole body F-FDG PET/CT imaging was sensitive for detecting primary sites/lesions with hepatic metastatases of unknown primary, especially when the SUVmax of hepatic metastases were greater than 4.7.

Metastatic neuroendocrine tumor masquerading as liver abscesses

Fever and deranged transaminases with liver mass(es) on imaging mandates further evaluation of the mass(es) and should be followed radiologically and clinically. In the absence of a definitive diagnosis, repeat biopsy should be done.

Atypic large hepatic cyst with persistent elevated CA19.9 serum value: utility of intracystic CA72.4 dosage for a mini-invasive management

Simple hepatic cysts are very common, but may be difficult to differentiate from a biliary cystadenoma or cystadenocarcinoma. Because the surgical treatment if needed, such as a hepatic fenestration or resection, depends on the diagnosis, the assay of intracystic tumor markers is useful.We report the case of a 67-year-old woman with a large hepatic cyst responsible of pain and inflammation. The combination of imaging findings, serum, and intracystic fluid tumor markers [CA72.4 (carbohydrate hydrogen)] permitted to diagnose a simple hepatic cyst despite an unusual persistent elevated serum CA19.9 level. A laparoscopic cyst fenestration was proposed with an uneventful postoperative course. The pathological findings showed a simple hepatic cyst.In case of hepatic cysts, radiological findings can discriminate between benign and (pre)malignant lesions, but in case of doubtful diagnosis, the serum and intracystic tumor markers can be helpful.The use of serum or intracystic tumor marker allows to choose the correct therapeutic strategy and to use mini-invasive approach when feasible.

PET/MRI of the hepatobiliary system: Review of techniques and applications

Simultaneous positron emission tomography and MRI (PET/MRI) is an emerging technology that offers the benefits of MRI, including excellent soft tissue contrast, lack of ionizing radiation, and functional MRI techniques, with the physiologic information provided by PET. Although most PET/MRI systems are currently installed in tertiary care centers, PET/MRI technology is becoming increasingly widespread. The usefulness of PET/MRI varies by tumor type and organ system and has been shown to have utility in evaluation of primary and secondary hepatic neoplasms. Understanding the appropriate applications, techniques and relevant imaging findings is important for practicing radiologists considering or currently utilizing PET/MR for the evaluation of primary liver neoplasms, including hepatocellular carcinoma (HCC), as well as staging of biliary neoplasms including cholangiocarcinoma and gallbladder cancer, identification of liver metastases, and staging of neuroendocrine tumor.

Imaging characteristics and prognostic values of hepatic epithelioid hemangioendothelioma on 18F-FDG PET/CT

Hepatic epithelioid hemangioendothelioma (HEHE) is a low-to-intermediate-grade malignant mesenchymal tumor. The diagnostic and prognostic values of 2-[18F] fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) to patients with HEHE have not been fully validated. Patient survival outcomes (including overall survival [OS] and progression-free survival [PFS]), lesions characteristics and semi-quantitative parameters, in terms of maximum standardized uptake value (SUV_max), peak SUV (SUV_peak), total lesion glycolysis (TLG) and metabolic tumor volume (MTV) on ¹⁸F-FDG PET/CT of 20 cases with HEHE were measured and analyzed. A total of 310 liver lesions were detected (excluding the diffuse-type lesions in 3 cases). Most lesions had higher SUV_max in delayed imaging than in early imaging (P = 0.013). Patients with multiple organs involved had higher death rate (P = 0.022), higher progression rate (P = 0.020), shorter OS (P = 0.011), larger lesion SUV_max (P = 0.048) and TLG (P = 0.033) than those with only liver involved. The area under curves (AUCs) from the receiver operating characteristic (ROC) curve analysis were 0.960, 0.949, 0.980 and 0.960 for SUV_max, SUV_peak, TLG and MTV, respectively, in predicting OS (P = 0.005, 0.008, 0.001 and 0.024, respectively). For predicting PFS, the AUCs were 0.791, 0.824, 0.857 and 0.813 (P = 0.036, 0.019, 0.010 and 0.024), respectively. Dual-time-point imaging may improve lesions detectability. Patients with multiple organ involved had worse prognosis. The higher SUV_max, SUV_peak, TLG and MTV of lesions, the worse prognosis of patients were found.

FDG-PET/CT imaging findings of hepatic tumors and tumor-like lesions based on molecular background

The usefulness of whole-body 18-fluoro-2-deoxyglucose (FDG)-fluorodeoxyglucose positron emission (PET)/computed tomography (CT) is established for assessment of disease staging, detection of early disease recurrence, therapeutic evaluation, and predicting prognosis in various malignancies; and for evaluating the spread of inflammation. However, the role of FDG-PET/CT for the liver is limited because CT and magnetic resonance imaging (MRI) can provide an accurate diagnosis of most tumors. In addition, in other potentially useful roles there are several pitfalls in the interpretation of FDG uptake in PET/CT imaging. Accurate evaluation demands knowledge of the FDG uptake of each lesion, including potential negative and positive uptakes, and requires an understanding of the underlying background of the molecular mechanisms. The degree of FDG uptake is dependent on cellular metabolic rate and the expression of glucose transporter, hexokinase, and glucose-6-phosphatase, which in turn are closely affected by biological characteristics such as pathological category (e.g., adenocarcinoma, squamous cell carcinoma, small cell cancer, transitional cell cancer, neuroendocrine tumor, sarcoma, lymphoma), tumor differentiation, histological behavior (e.g., solid, cystic, mucinous), and intratumoral alterations (e.g., necrosis, degeneration, hemorrhage). Correlation with the CT and MRI findings, which also precisely depict the pathological findings, is important to avoid misdiagnosis.

Three-Dimensional Texture Analysis Based on PET/CT Images to Distinguish Hepatocellular Carcinoma and Hepatic Lymphoma

Objectives: This study compared the diagnostic ability of image-based parameters with texture parameters in the differentiation of hepatocellular carcinoma (HCC) and hepatic lymphoma (HL) by positron emission tomography–computed tomography (PET/CT).

Methods: Patients with pathological diagnosis of HCC and HL were included in this study. Image-based and texture parameters were obtained by manual drawing of region of interest. Receiver operating characteristic (ROC) was used to test the diagnostic capacity of each parameter. Binary logistic regression was used to transform the most discriminative image-based parameters, texture parameters, and the combination of these parameters into three regression models. ROC was used to test the diagnostic capacity of these models.

Result: Ninety-nine patients diagnosed with HCC (n = 76) and HL (n = 23, 10 primary HL, 13 secondary HL) by histological examination were included in this study (From 2011 to 2018, West China hospital). According to the AUC and p-value, 2 image-based parameters and five texture parameters were selected. The diagnostic ability of texture-based model was better than that of image-based model, and after combination of those two groups of parameters the diagnostic capacity improved.

Conclusion: Texture parameters can differentiate HCC from HL quantitatively and improve the diagnostic ability of image-based parameters.

Fascioliasis presenting as colon cancer liver metastasis on 18F-fluorodeoxyglucose positron emission tomography/computed tomography: A case report

BACKGROUND

Fascioliasis is caused by watercress and similar freshwater plants or drinking water or beverages contaminated with metacercariae. Fascioliasis can radiologically mimic many primary or metastatic liver tumors. Herein, we aimed to present the treatment process of a patient with fascioliasis mimicking colon cancer liver metastasis.

CASE SUMMARY

A 35-year-old woman who underwent right hemicolectomy due to cecum cancer was referred to our clinic for management of colon cancer liver metastasis. Both computed tomography and ¹⁸F-fluorodeoxyglucose positron emission tomography revealed several tumoral lesions localized in the right lobe of the liver. After a 6-course FOLFOX (folinic acid, fluorouracil, oxaliplatin) and bevacizumab regimen, the hypermetabolic state on both liver and abdominal lymph nodes continued, and chemotherapy was extended to a 12-course regimen. The patient was referred to our institute when the liver lesions were detected to be larger on dynamic liver magnetic resonance imaging 6 weeks after completion of chemotherapy. Right hepatectomy was performed, and histopathological examination was compatible with fascioliasis. Fasciola hepatica IgG enzyme-linked immunosorbent assay was positive. The patient was administered two doses of triclabendazole (10 mg/kg/dose) 24 h apart. During the follow-up period, dilatation was detected in the common bile duct, and Fasciola parasites were extracted from the common bile duct by endoscopic retrograde cholangiopancreatography (ERCP). Triclabendazole was administered to the patient after ERCP.

CONCLUSION

Parasitic diseases, such as those caused by Fasciola hepatica, should be kept in mind in the differential diagnosis of primary or metastatic liver tumors, such as colorectal cancer liver metastasis, in patients living in endemic areas.

What, where and why: exploring fluorodeoxyglucose-PET's ability to localise and differentiate infection from cancer

PURPOSE OF REVIEW

To review the utility of FDG-PET imaging in detecting the cause of fever and infection in patients with cancer.

RECENT FINDINGS

FDG-PET has been shown to have high sensitivity and accuracy for causes of neutropenic fever, leading to higher diagnostic certainty in this group. Recent advances in pathogen-specific labelling in PET to identify Aspergillus spp. and Yersinia spp. infections in mice, as well as differentiating between Gram-positive, Gram-negative and mycobacterial infections are promising.

SUMMARY

Patients with cancer are vulnerable to infection and fever, and the causes of these are frequently unclear using conventional diagnostic methods leading to high morbidity and mortality, length of stay and costs of care. FDG-PET/CT, with its unique complementary functional and anatomical information as well as its whole-body imaging capability, has demonstrated use in detecting occult infection in immunocompromised patients, including invasive fungal and occult bacterial infections, as well as defining extent of infection. By demonstrating disease resolution following treatment and allowing earlier cessation of therapy, FDG-PET acts as a key tool for antimicrobial and antifungal stewardship. Limitations include at times poor differentiation between infection, malignancy and sterile inflammation, however, exciting new technologies specific to infectious pathogens may help alleviate that issue. Further prospective randomised research is needed to explore these benefits in a nonbiased fashion.

Evidence-based management of incidental focal uptake of fluorodeoxyglucose on PET-CT

Focal incidental uptake, with or without CT abnormalities, is a common finding on fluorodeoxyglucose PET/CT and evidence-based management for this type of uptake is lacking. This article reviews the evidence on focal incidental uptake including the incidence of malignancy, differential diagnosis and imaging criteria which can be used to further characterize it. The article focusses on PET rather than CT criteria. The strength of the evidence base is highly variable ranging from systematic reviews and meta-analyses to a virtual absence of evidence. Caution needs to be used when using standardized uptake values (SUVs) reported in other studies due to interpatient and institution observed variation in SUVs. There is sufficient evidence to permit specific suggestions on how to interpret the foci and recommend further management in the: pituitary (investigate when SUVmax >4.1), thyroid (investigate all), breast (investigate all), lung parenchyma (if focus of fluorodeoxyglucose without a CT nodule, no further investigations), colon (investigate all foci with SUVmax >5.9, urgently if SUVmax >11.4), adrenals (criteria depend on if patient has cancer) and prostate gland (investigate in males aged >50 years or >40 years if peripheral uptake or patient has other risk factors). There is some evidence to guide further management for the parotid gland, naso-orophaynx, oesophagus, pancreas, uterus and ovaries. There is insufficient evidence to guide management for the liver, spleen, kidneys, gallbladder, testis and bone, for these organs patient characteristics and other guidelines will likely be of more use in determining further management.

Liver metastases: Detection and staging

The liver is more often involved with metastatic disease than primary liver tumors. The accurate detection and characterization of liver metastases are crucial since patient management depends on it. The imaging options, mainly consisting of contrast-enhanced ultrasound (CEUS), multidetector computed tomography (CT), magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI), extra-cellular contrast media and liver-specific contrast media as well as positron emission tomography/computed tomography (PET/CT), are constantly evolving. PET/MRI is a more recent hybrid method and a topic of major interest concerning liver metastases detection and characterization. This review gives a brief overview about the spectrum of imaging findings and focus on an update about the performance, advantages and potential limitations of each modality as well as current developments and innovations.

18-Fluoro-deoxyglucose uptake in inflammatory hepatic adenoma: A case report

Positron emission tomography computed tomography (PET-CT) using 18-Fluoro-deoxyglucose (¹⁸FDG) is an imaging modality that reflects cellular glucose metabolism. Most cancers show an uptake of ¹⁸FDG and benign tumors do not usually behave in such a way. The authors report herein the case of a 38-year-old female patient with a past medical history of cervical intraepithelial neoplasia and pheochromocytoma, in whom a liver lesion had been detected with PET-CT. The tumor was laparoscopically resected and the diagnosis of inflammatory hepatic adenoma was confirmed. This is the first description of an inflammatory hepatic adenoma with an ¹⁸FDG up-take.

[Increased glucose uptake by seborrheic keratosis on PET scan]

BACKGROUND

Positron emission tomography (PET) is an examination based upon the uptake of a radioactive tracer by hypermetabolic cells. It is primarily used in tandem with tomodensitometry (PET-TDM) for cancer staging because of its high sensitivity and specificity for the detection of metastases. However, unusually high uptake may occur with benign tumours, including skin tumours. Herein, we report an extremely rare case of pathological uptake levels resulting from seborrhoeic keratosis.

PATIENTS AND METHODS

A 55-year-old male patient with oesophageal squamous-cell carcinoma was referred to us following the discovery of an area of high marker uptake following PET-TDM and corresponding to a pigmented skin lesion. No other areas of suspect high uptake were seen. The lesion was surgically excised and histological examination indicated seborrhoeic keratosis. The histological appearance was that of standard seborrhoeic keratosis without any notable mitotic activity.

DISCUSSION

PET-TDM is an examination that enables diagnosis of malignancy. However, rare cases have been described of increased marker uptake by benign cutaneous tumours such as histiocytofibroma, pilomatricoma and condyloma. To date, there have only been only very few cases of increased uptake due to seborrhoeic keratosis.

CONCLUSION

This extremely unusual case of increased glucose uptake in PET-TDM due to seborrhoeic keratosis confirms that the hypermetabolic activity detected by this examination is not necessarily synonymous with malignancy and that confirmation by clinical and histological findings is essential. The reasons for increased metabolic activity within such benign tumours are not known.

Fasciola Hepatica Mimicking Malignancy on 18F-Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography

A 48-year-old female with complaints of gastrointestinal symptoms such as abdominal pain, fatigue, vomiting, nausea, and weight loss was diagnosed with neuroendocrine tumor after removal of a 2 mm lesion from the stomach with endoscopic biopsy. Her magnetic resonance imaging that was performed due to on-going symptoms showed multiple linear hypointense lesions in the liver. Positron emission tomography/computed tomography (PET/CT) scan was performed for differential diagnosis, which showed high fluorodeoxyglucose (FDG) uptake in these lesions. Clinical and laboratory findings revealed the final diagnosis as Fasciola hepatica. The imaging features of this case is presented to aid in differentiating this infectious disease from malignancy and avoid misdiagnosis on FDG-PET/CT.

Tumor-Like Liver Abscess Mimicking Malignancy With Lung Metastases in a Patient With Acute Renal Failure: A Case Report

The worldwide incidence of Klebsiella pneumoniae liver abscess (KLA) is increasing. It is important to accurately diagnose this life-threatening disease to provide timely and appropriate treatment. Here we report the case of a 38-year-old man with acute renal failure and a tumor-like liver abscess and septic pulmonary embolism. Initially, his clinical symptoms, laboratory tests, and radiological findings presented equivocal results of malignancy with metastases. Fine needle aspiration of liver tumor was performed, which showed purulent material with a culture positive for K pneumoniae. KLA symptoms are atypical, and radiological findings may mimic a malignancy with tumor necrosis. In some circumstances, liver aspiration biopsy may be necessary to confirm the real etiology, leading to prompt and timely treatment. Moreover, we should be alert for the impression of KLA when facing a diabetic patient with liver mass lesion and acute renal failure.

Focally Increased FDG Activity in the Liver Related to Hydropic Degeneration

A 50-year-old man, who had diffuse large B-cell lymphoma in the neck and just finished 4 cycles of chemotherapy, presented to our department to evaluate the status of the disease. FDG PET/CT revealed a focally increased activity in the right lobe of the liver. However, pathological examination showed hepatocyte hydropic degeneration with associated inflammatory cells without evidence of malignancy.

18F-FDG PET/CT Findings in Portal Vein Thrombosis and Liver Metastases

(18)F-FDG PET/CT is a valuable noninvasive tool in oncologic imaging, and its application in the diagnosis of liver metastases has been very convincing. Both the sensitivity and the specificity of (18)F-FDG PET/CT are high for detecting liver metastases from various tumors including colorectal, breast, and lung. Such liver metastases are typically (18)F-FDG-avid. We present atypical (18)F-FDG PET findings in a lung cancer patient with known liver metastases and PVT.

Subdiaphragmatic gallstone mimicking hepatic malignancy on FDG PET/CT

A 70-year-old man underwent an FDG PET/CT for a possible primary liver malignancy or metastasis found on an abdominal MRI obtained as part of a workup for intermittent abdominal pain. The MRI showed an enhancing lesion at the dome of the right lobe of the liver. The lesion was FDG avid with a discrete central calcification. In conjunction with the patient's history of laparoscopic cholecystectomy 1 year prior, the findings were consistent with inflammation around a migrated subdiaphragmatic gallstone. One month after the scan, a CT-guided percutaneous biopsy of this lesion revealed chronic inflammatory cells with no evidence of malignancy.

Case report: adrenal oncocytoma associated with markedly increased FDG uptake and immunohistochemically positive for GLUT1

Usually, benign tumors are not associated with an increased F-18 fluorodeoxyglucose (F-18 FDG) uptake on positron emission tomography (PET), although some exceptions have been reported in adrenal neoplasms. We present a rare case of adrenocortical oncocytoma associated with markedly increased FDG uptake, demonstrating a maximum standardized uptake value of 46.8. Histological examination demonstrated diffuse proliferation of tumor cells with eosinophilic and granular cytoplasm that were diffusely immunopositive for mitochondria and glucose transport protein 1, with focal and weak immunopositivity for 3β-hydroxysteroid dehydrogenase. Ultrastructural examination also revealed abundant mitochondria in the tumor cells. The tumor was diagnosed as adrenocortical oncocytoma and was considered benign according to Lin-Weiss-Bisceglia criteria. Diagnosis of adrenocortical oncocytoma can pose difficulties during both preoperative radiological and postoperative histopathological investigations.