Oncocytic carcinoid tumor of the lung with intense F-18 fluorodeoxyglucose (FDG) uptake in positron emission tomography-computed tomography (PET/CT).

The present report describes a case of typical carcinoid tumor with intense fluorodeoxyglucose (FDG) uptake. The most of tumor cells were characterized by eosinophilic cytoplasm resulting from accumulation of mitochondria, which was called an oncocytic carcinoid tumor. Glucose transporter type 1 (GLUT-1) was expressed in a membranous pattern in the oncocytic component. Oncocytic carcinoid tumors could show intense FDG uptake due to the numerous intracellular mitochondria and the membranous overexpression of GLUT-1. Thus, it could be a potential pitfall of interpreting FDG-PET/CT image.

Differentiation of tumor recurrence from radiation-induced pulmonary fibrosis after stereotactic ablative radiotherapy for lung cancer: characterization of 18F-FDG PET/CT findings.

OBJECTIVE: Stereotactic ablative radiotherapy (SABR), also known as stereotactic body radiotherapy (SBRT), is now a standard treatment option for patients with stage I non-small cell lung cancer or oligometastatic lung tumor who are medically inoperable or medically operable but refuse surgery. When mass-like consolidation is observed on follow-up CT after SABR, it is sometimes difficult to differentiate tumor recurrence from SABR-induced pulmonary fibrosis. In this study, we evaluated the role of (18)F-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) in differentiating tumor recurrence from radiation fibrosis after SABR. METHODS: Between June 2006 and June 2009, 130 patients received SABR for stage I non-small cell lung cancer or metastatic lung cancer at our institution. Fifty-nine patients of them were imaged with FDG-PET/CT after SABR. There were a total of 137 FDG-PET/CT scans for retrospective analysis. The FDG uptake in the pulmonary region was assessed qualitatively using a 3-point scale (0, none or faint; 1, mild; or 2, moderate to intense), and the shape (mass-like or non mass-like) was evaluated. For semi-quantitative analysis, the maximum standardized uptake value (SUV(max)) was calculated. RESULTS: Sixteen of 59 patients had local failure. In recurrent tumor, the combination of intensity grade 2 and mass-like shape was most common (21/23; 91%). By contrast, in cases of radiation fibrosis, the combination of intensity grade 0 or 1 and non mass-like shape was most common (48/59; 81%). The SUV(max) of tumor recurrence after 12 months was significantly higher than that of radiation fibrosis (8.0 ± 3.2 vs. 2.1 ± 0.9, p < 0.001), and all tumor recurrence showed the SUV(max) > 4.5 at diagnosis of local failure. At ≥12 months after SABR, these two variables, the combination of intensity 2 and mass-like FDG uptake or SUV(max) > 4.5 acquired a significant high predictive value of local recurrence, finding sensitivity 100% and specificity 100% for both of them. CONCLUSIONS: The combination of FDG uptake patterns and SUV(max) was useful for distinguishing tumor recurrence from radiation fibrosis after SABR.

Incidence and characteristics of uterine leiomyomas with FDG uptake.

OBJECTIVE: Uterine leiomyomas sometimes show focal 18F-fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET) images that may result in a false-positive diagnosis for malignant lesions. This study was conducted to investigate the incidence and characteristics of uterine leiomyomas that showed FDG uptake. METHODS: We reviewed FDG-PET and pelvic magnetic resonance (MR) images of 477 pre-menopausal (pre-MP, age 42.1 +/- 7.3 years) and 880 post-MP (age 59.9 +/- 6.8 years) healthy women who underwent these tests as parts of cancer screening. Of 1357, 323 underwent annual cancer screening four times, 97 did three times, 191 did twice, and the rest were screened once. Focal FDG uptake (maximal standardized uptake value > 3.0) in the pelvis was localized and characterized on co-registered PET/MR images. RESULTS: Uterine leiomyomas were found in 164 pre-MP and 338 post-MP women. FDG uptake was observed in 18 leiomyomas of 17 of the 164 (10.4%) pre-MP women and in 4 leiomyomas of 4 of the 338 (1.2%) post-MP women. The incidence was significantly higher in pre-MP women than in post-MP women (chi-square, P < 0.001). Of the 22, 13 showed signal intensity equal to or higher than that of the myometrium on T2-weighted MR images, which suggested abundant cellularity, whereas the majority of leiomyomas without FDG uptake showed low signal intensity. Of the 13 women, 12 examined more than twice showed substantial changes in the level of FDG uptake in leiomyomas each year with FDG uptake disappearing or newly appearing. These changes were observed frequently in relation with menopause or menstrual phases. CONCLUSIONS: Leiomyomas with focal FDG uptake were seen in both pre-and post-MP women with a higher incidence in pre-MP women. Abundant cellularity and hormonal dependency may explain a part of the mechanisms of FDG uptake in leiomyomas. It is important to know that the level of FDG uptake in leiomyomas can change and newly appearing FDG uptake does not necessarily mean malignant transformation.

Visualization of treatment response in tumors by use of dynamic contrast-enhanced magnetic resonance imaging.

Our goal in this study was to present a method for generating functional parametric maps of hemodynamic parameters in tumors and a visualization method for assessing treatment response by use of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). A total of 13 patients with musculoskeletal tumors were included in this study. First, tumor blood flow (F(T)) maps were generated from DCE-MRI data by use of deconvolution analysis, and K(1), k(2), and f were obtained from a two-compartment model, where K(1) and k(2) denote the rate constant for the transfer of contrast agent from blood to tissue and from tissue to blood, respectively, and f is the fraction of the blood volume. Images were generated by application of the linear least squares method pixel by pixel. Furthermore, the images of the distribution volume (V(d)) and permeability-surface area product (PS) were obtained from the relations V(d) = K(1)/k(2) and PS = -F(T) x ln(1 - K(1)/(F(T)), respectively. Second, two-dimensional (2D) plots were generated with V(d) and K(1) placed on the x- and y-axes, and three-dimensional (3D) plots were generated by the addition of PS on the z-axis. In the case of good responders whose biopsied specimens revealed tumor necrosis greater than 90%, both 2D and 3D plots gradually approached the origin after an increasing number of treatments. On the other hand, in the case of non-responders whose biopsied specimens showed little chemotherapeutic effect, large changes were not observed in either plot. In conclusion, our method will be promising for evaluating the treatment response in tumors visually.

Evaluation of tumor blood flow in musculoskeletal lesions: dynamic contrast-enhanced MR imaging and its possibility when monitoring the response to preoperative chemotherapy-work in progress.

PURPOSE: The objective of this study was to calculate tumor blood flow (TBF) in musculoskeletal lesions and to evaluate the usefulness of this parameter in differentiating malignant from benign lesions and monitoring the treatment response to preoperative chemotherapy. MATERIALS AND METHODS: Altogether, 33 patients with musculoskeletal lesions underwent a total of 50 dynamic magnetic resonance imaging (MRI) examinations, including 28 on 9 patients undergoing preoperative chemotherapy. TBF was calculated using deconvolution analysis. Steepest slope (SS) was determined from the time-intensity curve during the first pass of contrast medium. RESULTS: TBF ranged from 2.7 to 178.6 mL/100 mL/min in benign lesions and from 15.4 to 296.3 mL/100 mL/min in malignant lesions. SS ranged from 0.5%/s to 31.8%/s for benign lesions and from 3.1%/s to 64.8%/sec for malignant lesions. TBF and SS did not differ significantly between benign and malignant lesions. Among the nine patients who underwent preoperative chemotherapy, TBF after chemotherapy was lower in good responders (11.7, 11.0, 7.9 mL/100 mL/min) (n = 3, tumor necrosis > or =90%) than in poor responders (23.4-141.5 mL/100 mL/min) (n = 6, tumor necrosis <90%). CONCLUSION: TBF and SS cannot reliably differentiate malignant from benign lesions. However, they have potential utility in evaluating the preoperative treatment response in patients with malignant musculoskeletal tumors.

Measurement of tumor blood flow using dynamic contrast-enhanced magnetic resonance imaging and deconvolution analysis: a preliminary study in musculoskeletal tumors.

OBJECTIVE: To measure tumor blood flow (TBF) using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). METHODS: A DCE-MRI was performed using inversion recovery-preparation fast-field echo sequences. Dynamic data were obtained every 3.2 seconds for 2 minutes, immediately after gadolinium injection. In 14 patients with malignant musculoskeletal tumors, TBF maps were generated pixel-by-pixel by deconvolution analysis. For preclinical studies, muscle blood flow in 5 volunteers and signal intensities of different gadolinium concentrations were measured. RESULTS: There was a good linear relationship between signal intensities and gadolinium concentrations (r = 0.989, P < 0.001, at gadolinium concentrations

Subcutaneous fibrolipoma in the back.

A 65-year-old man presented with a subcutaneous giant mass in his upper back. The tumor had a massive fatty and non-adipose component that enhanced heterogeneously on contrast-enhanced computed tomography and magnetic resonance imaging. Therefore, the lesion was initially thought to be a liposarcoma or spindle cell lipoma. After surgery, the tumor was histologically diagnosed as a fibrolipoma. Subcutaneous fibrolipoma is a rare neoplasm that is defined as a subtype of lipoma.

Thallium-201 scintigraphy in bone and soft-tissue tumors: a comparison of dynamic, early and delayed scans.

OBJECTIVE: It has been reported that delayed scan of thallium-201 (201Tl) scintigraphy is useful for differentiating malignant tumors from benign lesions and for evaluating treatment response. However, physiological muscle uptake which usually increases in delayed scans, often makes it difficult to evaluate 201Tl uptake and its washout in bone and soft-tissue tumors. The purpose of this study was to evaluate whether the delayed scan is necessary and whether a dynamic scan is useful in the evaluation of bone and soft-tissue tumors. METHODS: We studied 175 cases of bone and soft-tissue tumors (malignant 45, benign 130). Dynamic scans were acquired every 5 seconds for 10 minutes after 201Tl injection, and time activity curves (TACs) were generated by adaptive smoothing methods. Early and delayed scans were acquired at 10-15 minutes and 2 hours after injection. 201Tl images were visually interpreted and the radioactivity count ratio (T/N) of tumors to normal tissues and washout rate [WR = (early T/N - delayed T/N)/early T/N] were defined. RESULTS: When there were no 201Tl uptake in dynamic (n = 67) and early scans (n = 68), no tumor uptake was also appreciated in delayed scans, and all but two cases of negative scans were benign. In 107 lesions, although there were significant differences in T/Ns between malignant and benign lesions both on early scans (2.84 +/- 1.45 vs. 2.05 +/- 1.13, p < 0.05) and delayed scans (2.17 +/- 1.03 vs. 1.58 +/- 0.64, p < 0.05), there was a substantial overlap. The T/Ns decreased in delayed scans (i.e., WR > 0) in 100 of 107 cases due to increase of surrounding muscle uptake, and there was no difference in WR between malignant tumors and benign lesions (0.21 +/- 0.14 vs. 0.19 +/- 0.14). CONCLUSIONS: For evaluating bone and soft-tissue tumors, delayed scan had little clinical usefulness and it may be time consuming. Dynamic scan would be useful for demonstrating the differences between tumor blood flow and 201Tl uptake in tumors.

Healing focal "flare" phenomenon after radiotherapy in a bone metastasis from bladder cancer.

"Flare" phenomenon has been primarily reported as a transient increase in the number or intensity of lesions on bone scans in patients receiving hormonal or chemotherapy. It has been well documented in patients with metastatic breast or prostate carcinoma, and recently reported in those with lung cancer. We present a case of bone metastasis from bladder carcinoma, in which healing flare phenomenon was observed after radiotherapy.

Tl-201 and Tc-99m HMDP scintigraphic findings in extraskeletal osteosarcoma.

Extraskeletal osteosarcoma is an extremely rare high-grade malignant soft tissue tumor, which accounts for approximately 4% of osteosarcomas and less than 1% of all soft tissue sarcomas. There have been reports describing the scintigraphic findings of this tumor, especially with Tl-201. We report a biopsy-proven case of extraskeletal osteosarcoma in which the bone and thallium scans were found to be useful in monitoring chemotherapy response. The Tc-99m HMDP bone scan revealed increased extraskeletal uptake in the tumor.

Extraskeletal osteosarcoma in the thigh: a case report.

Extraskeletal osteosarcoma is a rare malignant soft-tissue tumor. There are few reports describing the radiological findings of this tumor, especially concerning its MRI and scintigraphic appearance. We report a 58-year-old man with extraskeletal osteosarcoma in the thigh. Radiographs showed small foci of mineralization in the mass. The tumor showed low intensity on T1-weighted images and predominantly high intensity on T2-weighted images, and the tumor was heterogeneously well enhanced on Gd-DTPA-enhanced T1-weighted images. Bone scintigraphy showed extraskeletal uptake in the tumor, and thallium-201 scintigraphy revealed marked inhomogeneous accumulation.