Clinicopathological presentation of varying 18F-FDG uptake and expression of glucose transporter 1 and hexokinase II in cases of hepatocellular carcinoma and cholangiocellular carcinoma

We report the results of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG PET) and immunohistochemical staining of glucose transporter 1 (Glut-1) and hexokinase II (HK-II) in patients with hepatocellular carcinoma (HCC) and cholangiocellular carcinoma (CCC) to observe the variation in ¹⁸F-FDG uptake and variation in expression of Glut-1 and HK-II in these hepatic tumors. In the case of HCC, moderate ¹⁸F-FDG uptake and strong expression of HK-II were detected, whereas Glut-1 was not expressed. Conversely, CCC showed high ¹⁸F-FDG uptake and increased expression of Glut-1 but HK-II was not expressed. The variation in the ¹⁸F-FDG uptake and expression of Glut 1 and HK-II in HCC and CCC might be owing to the difference in origin and the different mechanisms involved in glucose uptake, rate of glucose transporters, and hexokinase activity involved in the glycolytic pathway.     

Biologic correlates of intratumoral heterogeneity in 18F-FDG distribution with regional expression of glucose transporters and hexokinase-II in experimental tumor.

The biologic mechanisms involved in the intratumoral heterogeneous distribution of 18F-FDG have not been fully investigated. To clarify factors inducing heterogeneous 18F-FDG distribution, we determined the intratumoral distribution of 18F-FDG by autoradiography (ARG) and compared it with the regional expression levels of glucose transporters Glut-1 and Glut-3 and hexokinase-II (HK-II) in a rat model of malignant tumor. METHODS: Rats were inoculated with allogenic hepatoma cells (KDH-8) into the left calf muscle (n = 7). Tumor tissues were excised 1 h after the intravenous injection of 18F-FDG and sectioned to obtain 2 adjacent slices for ARG and histochemical studies. The regions of interest (ROIs) were placed on ARG images to cover mainly the central (CT) and peripheral (PT) regions of viable tumor tissues and necrotic/apoptotic (NA) regions. The radioactivity in each ROI was analyzed quantitatively using a computerized imaging analysis system. The expression levels of Glut-1, Glut-3, and HK-II were determined by immunostaining and semiquantitative evaluation. The hypoxia-inducible factor 1 (HIF-1) was also immunostained. RESULTS: ARG images showed that intratumoral 18F-FDG distribution was heterogeneous. The accumulation of 18F-FDG in the CT region was the highest, which was 1.6 and 2.3 times higher than those in the PT and NA regions, respectively (P < 0.001). The expression levels of Glut-1, Glut-3, and HK-II were markedly higher in the CT region (P < 0.001) compared with those in the PT region. The intratumoral distribution of 18F-FDG significantly correlated with the expression levels of Glut-1, Glut-3, and HK-II (r = 0.923, P < 0.001 for Glut-1; r = 0.829, P < 0.001 for Glut-3; and r = 0.764, P < 0.01 for HK-II). The positive staining of HIF-1 was observed in the CT region. CONCLUSION: These results demonstrate that intratumoral 18F-FDG distribution corresponds well to the expression levels of Glut-1, Glut-3, and HK-II. The elevated expression levels of Glut-1, Glut-3, and HK-II, induced by hypoxia (HIF-1), may be contributing factors to the higher 18F-FDG accumulation in the CT region.     

FDG PET for grading malignancy in thymic epithelial tumors: Significant differences in FDG uptake and expression of glucose transporter-1 and hexokinase II between low and high-risk tumors: Preliminary study

Purpose

To evaluate ¹⁸F-fluorodeoxyglucose (FDG) uptake to predict the malignant nature and analyze the correlation between FDG uptake and expression of glucose transporter 1 (Glut-1) and hexokinase II (HK-II) in thymic epithelial tumors.

Materials and methods

Eleven patients with a thymic epithelial tumor who underwent FDG PET/CT before therapy were reviewed. The thymic tumors were classified by the WHO histological classification and Masaoka clinical staging. Comparison of maximum standardized uptake value (SUV_max) of the lesion was made between the low-risk (Type A, AB and B1) and high-risk {Type B2, B3 and C (thymic cancer)} groups and among clinical stages. Expression of Glut-1 and HK-II was analyzed immunohistochemically.

Results

All 11 tumors showed FDG uptake visually. SUV_max was significantly higher in the high-risk group (n = 5, 5.24 ± 2.44) than the low-risk group (n = 6, 3.05 ± 0.55) (P = 0.008). Staining scores of both Glut-1 and HK-II were significantly higher in the high-risk group than in the low-risk group (Glut1: P = 0.034 and HK-II: P = 0.036). There were no significant differences in SUV_max (P = 0.11), Glut-1 (P = 0.35) and HK-II scores (P = 0.29) among clinical stages. SUV_max was significantly correlated to each of the staining scores of Glut-1 (ρ = 0.68, P = 0.031) and HK-II (ρ = 0.72, P = 0.024).

Conclusion

These preliminary results support the previously published view that SUV_max may be useful to predict the malignant nature of thymic epitherial tumors and suggest that the degree of FDG uptake in the thymic epitherial tumors is closely related to the amount of Glut-1 and HK-II in the tumor.     

18F-FDG uptake in squamous cell carcinoma of the cervix is correlated with glucose transporter 1 expression.

This prospective study investigates the relationship between glucose transporter-1 (Glut-1) expression and PET images using (18)F-FDG and its uptake and compares them with the tumor status (primary vs. recurrent or persistent), initial grade of histologic differentiation, and International Federation of Gynecologic Obstetrics (FIGO) staging for cervical cancer patients. METHODS: A dual-phase (18)F-FDG PET scan was performed on 51 participants within the 2 wk before surgery or biopsy. (18)F-FDG uptake was quantified by calculating standardized uptake values (SUVs). After (18)F-FDG PET scanning, 51 histologically proven squamous cell carcinoma specimens were examined to determine their degree of differentiation, using hematoxylin and eosin staining, and the expression of Glut-1 by an immunohistochemical stain. Twenty normal cervical and 20 cervical intraepithelial neoplasia (CIN) sets of tissue were also used to compare the results of Glut-1 expression in these tissues. The expression of Glut-1 was the product of (the intensity [with grades 0-3, defined qualitatively]) with (percentages of the lesion area that were positive). The results of Glut-1 expression were analyzed in combination with the SUVs (SUV1 was that at 40 min and SUV2 was that at 3 h), tumor status, initial cell differentiation, and FIGO staging. RESULTS: Significant overexpression of Glut-1 was noted in 48 of the 51 (94.1%) cancer specimens. None or only minimal expression of Glut-1 was observed in basal layers of normal and CIN tissues. Significant positive correlation was observed between Glut-1 expression and the SUVs in cervical cancer specimens (r = 0.74, P < 0.000 for SUV1 and r = 0.65, P < 0.000 for SUV2). In recurrent or persistent tumor, tumor size was significantly associated with both Glut-1 expression (r = 0.508, P = 0.011) and SUV1 (r = 0. 456, P = 0.025). For recurrent or persistent tumor, only SUV1 reached statistical significance when compared with lymph node metastasis (P = 0.0226). CONCLUSION: Glut-1 expression was related to (18)F-FDG uptake in cervical cancer patients. Recurrent or persistent cervical cancer tumor had significantly higher Glut-1 expression than metastatic lymph nodes. The values of SUV and the expression of Glut-1 did not correlate with the initial grade of histologic differentiation and FIGO staging.     

Relations Between Pathological Markers and Radioiodine Scan and 18F-FDG PET/CT Findings in Papillary Thyroid Cancer Patients With Recurrent Cervical Nodal Metastases

Purpose

The aim of this study was to investigate relationships between the immunohistochemical results and radioiodine scan and ¹⁸F-FDG PET findings in papillary thyroid cancer (PTC) patients with recurrent cervical nodal metastases.

Methods

A total of 46 PTC patients who had undergone a radioiodine scan and/or ¹⁸F-FDG PET/CT and a subsequent operation on recurrent cervical lymph nodes were enrolled. Twenty-seven patients underwent ¹⁸F-FDG PET/CT, 8 underwent radioiodine scans, and 11 underwent both scans. In all surgical specimens, the immunoexpressions of thyroglobulin (Tg), sodium-iodide symporter (NIS), glucose transporter 1 (Glut-1), and somatostatin receptor 1 and 2A (SSTR1 and SSTR2A) were assessed, and associations between these expressions and radioiodine scan and ¹⁸F-FDG PET findings were evaluated.

Results

Of the 38 patients who underwent ¹⁸F-FDG PET/CT, all patients with weak Tg expression had positive ¹⁸F-FDG uptake, while only 45 % of the patients with moderate or strong Tg expression showed positive uptake (p = 0.01). The proportion of patients with positive ¹⁸F-FDG uptake increased as the degree of Glut-1 expression with luminal accentuation increased. Of the 19 patients who underwent a radioiodine scan, the proportion with positive radioiodine uptake was greater among patients with strong NIS and SSTR2A expression than among patients expressing these markers at weak levels (p = 0.04 for all). All three patients with weak Tg expression were negative for radioiodine uptake.

Conclusion

The ¹⁸F-FDG uptakes of recurrent cervical nodes are related to strong Glut-1 expression with luminal accentuation and weak Tg expression, whereas radioiodine uptake is related to the strong expressions of NIS and SSTR2A.     

18F-FDG-PET of musculoskeletal tumors: a correlation with the expression of glucose transporter 1 and hexokinase II

Objective  It remains controversial whether positron emission tomography (PET) with 2-deoxy-2-[F-18]fluoro-d-glucose (F-18-FDG) can differentiate between benign and malignant musculoskeletal tumors. To uncover the mechanism of F-18-FDG accumulations, we analyzed the correlation between the F-18-FDG accumulation and the expression of glucose transporter 1 (Glut-1) and hexokinase II (HK-II) in benign and malignant musculoskeletal tumors. Methods  The maximum standardized uptake values (SUV_max) of F-18-FDG in 24 benign and 26 malignant musculoskeletal tumors were compared with the histologic malignancies, and the expression of Glut-1 and HK-II was analyzed by immunohistochemistry. Results  The SUV_max for malignant tumors (6.33 ± 4.79) was significantly higher than those with benign tumors (3.47 ± 3.12, P < 0.01). The expression of Glut-1 was high in 12 patients (all malignant) and low in 38 patients (24 benign and 14 malignant), and the expression of HK-II was high in 36 patients (11 benign and 25 malignant) and low in 14 patients (13 benign and 1 malignant). Cases with high expression of Glut-1 and HK-II at immunohistochemistry showed a higher SUV_max than those with low expression (Glut-1 8.03 ± 5.10 and 3.98 ± 3.53, P < 0.01; HK-II 5.73 ± 4.49 and 2.99 ± 3.02, P < 0.01). No significant dividing threshold of the SUV_max of F-18 FDG was found for the differential diagnosis between benign and malignant tumors or for the expression of Glut-1 and HK-II. Conclusions  The limited capability of F-18 FDG-PET in the differential diagnosis of musculoskeletal tumors is owing partly to the various levels of Glut-1 and HK-II expression in individual tumors.     

18F-FDG PET/CT Findings in a Breast Cancer Patient with Concomitant Tuberculous Axillary Lymphadenitis

Although ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) is a sensitive modality for detecting a malignant lesion, increased ¹⁸F-FDG uptake is also seen in infected or inflammatory processes. Here, we report the case of a breast cancer patient with concomitant tuberculous axillary lymphadenitis that showed increased ¹⁸F-FDG uptake. A 39-year-old woman underwent preoperative ¹⁸F-FDG PET/computed tomography (CT) as a part of the work-up for right breast cancer. ¹⁸F-FDG PET/CT images showed a malignant lesion in the right breast with moderate ¹⁸F-FDG uptake, and multiple enlarged right axillary lymph nodes with intense ¹⁸F-FDG uptake. Subsequently, the patient underwent right mastectomy and right axillary lymph node dissection. Histopathological examination confirmed breast cancer and tuberculous lymphadenitis, and the patient was treated concomitantly with anti-tuberculous therapy.     

Expressions of glucose transporter Types 1 and 3 and hexokinase-II in diffuse large B-cell lymphoma and other B-cell non-Hodgkin's lymphomas

IntroductionDiffuse large B-cell lymphoma (DLBCL) has been reported to show higher uptake of 2-deoxy-2-F18-fluoro-d-glucose (FDG) by positron emission tomography than other B-cell non-Hodgkin's lymphomas (non-DLBCL). The authors addressed the mechanism of FDG uptake in DLBCL by immunostaining for glucose transporter Types 1 (Glut-1) and 3 (Glut-3) and hexokinase-II (HK-II) in excised lymphoma tissues.MethodsSixteen B-cell non-Hodgkin's lymphoma patients (11 DLBCL and 5 non-DLBCL patients) were included in the study because the lymphoma tissues obtained by excision were eligible for immunostaining. The expressions of Glut-1, Glut-3 and HK-II were assessed regarding the percentages of positively stained lymphoma cells (%expression), the staining intensities (none=0, weak=1, moderate=2 and strong=3) and the staining patterns (membranous or cytoplasmic) and compared between DLBCL and non-DLBCL.ResultsGlut-1 was not expressed at all in DLBCL or non-DLBCL, and their Glut-3 expressions were not significantly different (P>.05) with respect to %expression (mean±S.E.M., 73.6±7.3% vs. 72.0±3.7%), staining intensity (2.5±0.2 vs. 2.6±0.2) and staining pattern (membranous pattern dominant; 54.5% vs. 60.0%). However, DLBCL expressed more HK-II than non-DLBCL, i.e., %expression (45.2±11.5% vs. 17.0±15.8%, P=.0275) and staining intensity (2.3±0.2 vs. 0.6±0.4, P=.0032). HK-II showed a cytoplasmic location in DLBCL and non-DLBCL.ConclusionsHK-II and Glut-3 contribute significantly to FDG uptake in DLBCL. DLBCL may have higher FDG uptake because it expresses more HK-II, whereas Glut-1 appears to play no role in FDG uptake in B-cell non-Hodgkin's lymphoma.     

Pseudomesotheliomatous lung cancer mimicking mesothelioma on 18F-FDG PET/CT images: report of 2 cases

The authors report two cases of pseudomesotheliomatous lung cancer (PLC) detected by ¹⁸F-FDG PET/CT scan. ¹⁸F-FDG PET/CT clearly revealed the extent of the disease in both cases, a case of adenocarcinoma of the lung and a case of squamous cell carcinoma of the lung. Intense ¹⁸F-FDG uptake by the diffusely thickened pleurae and primary lesion was observed in both cases, and increased ¹⁸F-FDG uptake by a pelvic bone metastasis was observed in the case of squamous cell carcinoma. Although PLC is indistinguishable from malignant pleural mesothelioma on ¹⁸F-FDG PET/CT scans, ¹⁸F-FDG PET/CT was helpful in identifying the primary focus of the PLCs and in staging the disease. Diagnostic image interpreters should be familiar with the ¹⁸F-FDG PET/CT findings in PLC.     

Primary Malignant Fibrous Histiocytoma in Mediastinum: Imaging with 18F-FDG PET/CT

Malignant fibrous histiocytoma (MFH) is the most common soft tissue tumor which often occurs in the extremities and the retroperitoneum. Primary mediastinal MFH is rare; thus, findings on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) of mediastinal MFH have not been reported yet. We report herein the case of a 64-year-old man who was presented with a superior mediastinal mass. The mass showed intense ¹⁸F-FDG uptake with central metabolic defect on PET/CT. The maximum standardized uptake value was 17.4. After tumor removal via median sternotomy, an MFH of the storiform-pleomorphic type was diagnosed on histopathologic examination. We present the first report of ¹⁸F-FDG PET/CT imaging of MFH in the superior mediastinum.     

Giant Cell Tumor with Secondary Aneurysmal Bone Cyst Shows Heterogeneous Metabolic Pattern on <Superscript>18</Superscript>F-FDG PET/CT: A Case Report

Giant cell tumor (GCT) is a generally benign bone tumor accounting for approximately 5 % of all primary bone neoplasms. Cystic components in GCTs that indicate secondary aneurysmal bone cysts (ABCs) are reported in 14 % of GCTs. Although both of them have been described separately in previous reports that may show considerable fluorodeoxyglucose (FDG) uptake despite their benign nature, the findings of GCT with secondary ABC on ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) have not been well-known. We report a case of GCT with secondary ABC in a 26-year-old woman. ¹⁸F-FDG PET/CT revealed a heterogeneous hypermetabolic lesion in the left proximal femur with the maximum standardized uptake value of 4.7. The solid components of the tumor showed higher FDG uptake than the cystic components. These observations suggest that the ABC components in GCTs show heterogeneous metabolic patterns on ¹⁸F-FDG PET/CT.     

Physiological 18F-FDG uptake in the ovaries and uterus of healthy female volunteers

Purpose Good knowledge of physiological ¹⁸F-fluorodeoxglucose (¹⁸F-FDG) uptake in the healthy population is of great importance for the correct interpretation of ¹⁸F-FDG positron emission tomography (PET) images of pathological processes. The purpose of this study was to investigate the physiological ¹⁸F-FDG uptake in the ovaries and uterus of healthy female volunteers.Methods One hundred and 33 healthy females, 78 of whom were premenopausal (age 37.2±6.9 years) and 55 postmenopausal (age 55.0±2.7 years), were examined using whole-body ¹⁸F-FDG PET and pelvic magnetic resonance (MR) imaging. Focal ¹⁸F-FDG uptake in the ovaries and uterus was evaluated visually and using standardised uptake value (SUVs). Anatomical and morphological information was obtained from MR images.Results Distinct ovarian ¹⁸F-FDG uptake with an SUV of 3.9±0.7 was observed in 26 premenopausal women out of 32 examined during the late follicular to early luteal phase of the menstrual cycle. Eighteen of the 32 women also showed focal ¹⁸F-FDG uptake in the endometrium, with an SUV of 3.3±0.3. On the other hand, all nine women in the first 3 days of the menstrual cycle demonstrated intense ¹⁸F-FDG uptake in the endometrium, with an SUV of 4.6±1.0. No physiological ¹⁸F-FDG uptake was observed in the ovaries or uterus of any postmenopausal women.Conclusion In women of reproductive age, ¹⁸F-FDG imaging should preferably be done within a week before or a few days after the menstrual flow phase to avoid any misinterpretation of pelvic ¹⁸F-FDG PET images.     

Intraosseous hemangioma arising in the clavicle

Intraosseous hemangioma (IH) is commonly seen in the vertebral column and skull: however, IH occurring in the appendicular skeleton, including the clavicle, is uncommon. We herein report the case of a 69-year-old female presenting with IH of the left clavicle. The findings of preoperative imaging studies, including radiographs, computed tomography (CT), magnetic resonance imaging, fluorine-18-fludeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/CT and ultrasonography, are described. In particular, ¹⁸F-FDG PET/CT showed an ill-defined osteolytic lesion with abnormally high FDG uptake. Surgical en bloc resection with preoperative embolization was carried out and a histopathological examination confirmed the presence of an intraosseous cavernous hemangioma in the clavicle.     

68Ga-DOTATATE-avid pulmonary sclerosing pneumocytoma in a man of North African descent: Case report,imaging findings and pathology

Pulmonary sclerosing pneumocytoma (PSP) is a benign tumor originating from primitive respiratory epithelium which tends to present as an asymptomatic solitary lesion in the periphery of the lung. It primarily occurs in women, with a 5:1 ratio of female to male, and in East Asian populations. We describe a rare case of a gallium-68 (⁶⁸Ga)-DOTATATE avid PSP in a middle-aged man of North African ancestry. Contrast-enhanced computed tomography (CT) revealed an enhancing ovoid 2-cm solid lesion within the periphery of the left upper lobe abutting the superior portion of the lateral left ventricular wall. A fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) demonstrated low-level FDG uptake, but a ⁶⁸Ga-DOTATATE PET/CT showed avid tracer uptake, concerning for a carcinoid tumor. The lesion was surgically excised, and the histopathologic analysis revealed the typical morphologic and histochemical markers of a PSP. We conclude that, although rare, PSP can be a differential consideration when evaluating a ⁶⁸Ga-DOTATATE-avid solitary lung nodule concerning for carcinoid tumor, in all genders and in ethnicities other than East Asian.     

Relationship between retention index in dual-phase (18)F-FDG PET, and hexokinase-II and glucose transporter-1 expression in pancreatic cancer.

Recently, some studies have shown that delayed scanning with (18)F-FDG PET may help to differentiate malignant from benign pancreatic lesions. However, no study has evaluated the relationship between temporal changes in (18)F-FDG uptake and expression of hexokinase or glucose transporter. METHODS: Twenty-one consecutive patients with pancreatic cancer were studied preoperatively by dual-phase (18)F-FDG PET, performed 1 and 2 h after injection of (18)F-FDG. The standardized uptake value (SUV) of the pancreatic cancer was determined, and the retention index (RI) (%) was calculated by subtracting the SUV at 1 h (SUV1) from the SUV at 2 h (SUV2) and dividing by SUV1. The percentages of cells strongly expressing hexokinase type-II (HK-II) and glucose transporter-1 (GLUT-1) were scored on a 5-point scale (1 = 0%-20%, 2 = 20%-40%, 3 = 40%-60%, 4 = 60%-80%, 5 = 80%-100%) by visual analysis of immunohistochemical staining of paraffin sections from the tumor specimens using anti-HK-II and anti-GLUT-1 antibody (HK-index and G-index, respectively). RESULTS: SUV2 (mean +/- SD, 5.7 +/- 2.6) was higher than SUV1 (5.1 +/- 2.1), with an RI of 8.5 +/- 11.0. Four cases of cancer, in which SUV2 showed a decline from SUV1, showed a low HK-index (1.8 +/- 1.1), whereas 4 cases with an RI of > or =20 and 13 cases with an intermediate RI (0-20) showed significantly higher HK-indices (4.3 +/- 0.7 and 3.1 +/- 1.5, respectively; P < 0.05). RI showed a positive correlation with HK-index, with an R(2) of 0.27 (P < 0.05), but no significant correlation with the G-index. SUV1 showed no relationship with the HK-index but showed a weak positive correlation with the G-index, with an R(2) of 0.05 (P = 0.055). CONCLUSION: These preliminary findings suggest that the RI obtained from dual-phase (18)F-FDG PET can predict HK-II expression and that the SUV (at 1 h) has a positive correlation with GLUT-1 expression but not with HK-II expression.     

<Superscript>18</Superscript>F-FDG PET/CT Imaging of Pulmonary Mucinous Cystadenocarcinoma with Signet Ring Cells

A 63-year-old male with a recently diagnosed right lung lesion was referred for staging. F-FDG PET/CT scan revealed a hypodense, cystic-like mass in the right upper lung lobe, which demonstrated low, diffuse ¹⁸F-FDG uptake, likely due to the presence of mucus, as well as intensely hypermetabolic right hilar and right paratracheal lymph nodes. Transbronchial biopsy revealed a primary pulmonary mucinous cystadenocarcinoma with the presence of signet ring cell carcinoma, a co-existence of two rare variants of lung adenocarcinoma. This case report demonstrates the metabolic phenotype along with the radiographic characteristics of this rare tumor and its metastases.     

Dynamic 18F-fluorodeoxyglucose positron emission tomography/CT in hibernoma: Enhanced tracer uptake mimicking liposarcoma

We report on two cases of patients with fat-equivalent masses in computed tomography (CT), referred to our department for dynamic positron emission tomography/CT (dPET/CT) with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) in order to investigate their dignity. Both qualitative and quantitative information, as derived from dPET/CTs, couldn’t exclude a high-grade liposarcoma: Visual evaluation, revealed a large hypermetabolic focus of intense ¹⁸F-FDG uptake in each patient (average SUVs 8.3 and 11.3). Regression-based parametric imaging demonstrated an enhanced distribution volume, which correlates to perfusion, and a high phosphorylation rate that correlates to cell viability. Kinetic analysis, based on a two-tissue compartment model demonstrated an enhanced FDG transport k₁ and an enhanced phosphorylation rate k₃. A non-compartmental approach based on fractal dimension revealed also enhanced values. However, final diagnosis was based on biopsy, which revealed hibernoma, a benign brown fat tumor. Brown adipose contains increased numbers of mitochondria and a high-rate of glucose metabolism. Therefore, they have increased FDG uptake. The evaluation of lipomatous lesions on CT, with high FDG uptake, should include the possibility of hibernoma as a differential diagnosis.     

Perirenal 18F-FDG Uptake in a Patient with a Pheochromocytoma

Increased ¹⁸F-fluorodeoxyglucose (FDG) uptake of brown fat on ¹⁸F-FDG positron emission tomography (PET) originating from physiological activation is a common incidental finding and is usually located in the neck, shoulder, and supraclavicular areas. We present a case of an incidental pheochromocytoma showing diffusely increased ¹⁸F-FDG uptake in bilateral perirenal fat tissue as well as supraclavicular and paravertebral fat tissue on ¹⁸F-FDG PET/CT. The patient had no clinical symptoms except hypertension, and a pheochromocytoma was confirmed in a postsurgical specimen. A pheochromocytoma should be considered a cause in cases of increased ¹⁸F-FDG uptake of perirenal brown fat.     

Comparison of F-FET and F-FDG PET in brain tumors

The purpose of this study was to compare the diagnostic value of positron emission tomography (PET) using [¹⁸F]-fluorodeoxyglucose (¹⁸F-FDG) and O-(2-[¹⁸F]fluoroethyl)-l-tyrosine (¹⁸F-FET) in patients with brain lesions suspicious of cerebral gliomas.

Methods

Fifty-two patients with suspicion of cerebral glioma were included in this study. From 30 to 50 min after injection of 180 MBq ¹⁸F-FET, a first PET scan (¹⁸F-FET scan) was performed. Thereafter, 240 MBq ¹⁸F-FDG was injected and a second PET scan was acquired from 30 to 60 min after the second injection (¹⁸F-FET/¹⁸F-FDG scan). The cerebral accumulation of ¹⁸F-FDG was calculated by decay corrected subtraction of the ¹⁸F-FET scan from the ¹⁸F-FET/¹⁸F-FDG scan. Tracer uptake was evaluated by visual scoring and by lesion-to-background (L/B) ratios. The imaging results were compared with the histological results and prognosis.

Results

Histology revealed 24 low-grade gliomas (LGG) of World Health Organization (WHO) Grade II and 19 high-grade gliomas (HGG) of WHO Grade III or IV, as well as nine others, mainly benign histologies. The gliomas showed increased ¹⁸F-FET uptake (>normal brain) in 86% and increased ¹⁸F-FDG uptake (>white matter) in 35%. ¹⁸F-FET PET provided diagnostically useful delineation of tumor extent while this was impractical with ¹⁸F-FDG due to high tracer uptake in the gray matter. A local maximum in the tumor area for biopsy guidance could be identified with ¹⁸F-FET in 76% and with ¹⁸F-FDG in 28%. The L/B ratios showed significant differences between LGG and HGG for both tracers but considerable overlap so that reliable preoperative grading was not possible. A significant correlation of tracer uptake with overall survival was found with ¹⁸F-FDG only. In some benign lesions like abscesses, increased uptake was observed for both tracers indicating a limited specificity of both techniques.

Conclusions

¹⁸F-FET PET is superior to ¹⁸F-FDG for biopsy guidance and treatment planning of cerebral gliomas. The uptake of ¹⁸F-FDG is associated with prognosis, but the predictive value is limited and a histological evaluation of tumor tissue remains necessary. Therefore, amino acids like ¹⁸F-FET are the preferred PET tracers for the clinical management of cerebral gliomas.     

Incidental finding of an <Superscript>11</Superscript>C-acetate PET-positive multiple myeloma

Multiple myeloma is a malignancy of plasma cells. The ¹⁸F-FDG PET findings of multiple myeloma have been reported previously. However, the ¹¹C-acetate PET findings have not been clarified. Here, we report a case of multiple myeloma detected with ¹¹C-acetate PET in a 51-year-old male patient with known hepatocellular carcinoma. The patient was admitted for management of a pathologic fracture of the right tibia. Imaging workup including X-ray, magnetic resonance image, bone scintigraphy; ¹⁸F-FDG led to a suspicion of metastatic bony lesions. Further, these lesions showed increased uptake on ¹¹C-acetate PET. Wide excision of the right tibia was performed, and histopathological examination of the lesion confirmed multiple myeloma. This case illustrates the characteristic ¹¹C-acetate PET findings of multiple myeloma.