Differential diagnosis of metastases in bone scans: chemotherapy induced bone necrosis.

AIM: Influenced by the incorrect diagnosis of a bone metastasis caused by bone necrosis we evaluated reasons and frequency of bone necrosis in patients referred for bone scanning in follow-up of tumors. METHODS: Bone scans performed within two years on patients with primary bone tumors or tumors metastatic to bone were reviewed in respect to the final diagnosis bone necrosis. RESULTS: We found the cases of three young patients who presented the appearance of hot spots on bone scintigrams which were finally diagnosed as bone necrosis. In two cases the diagnosis was based on histological findings, in one case the diagnosis was made evident by follow-up. All the three patients had been treated by chemotherapy and presented no other reason for the development of bone necrosis. Enhanced tracer uptake in all sites decreased within eight weeks up to two years without therapy. CONCLUSION: Single and multiple hot spots after chemotherapy may be originated by bone necrosis but mimicry metastases.

Fluorine-18 fluorodeoxyglucose positron emission tomography in thyroid cancer: results of a multicentre study.

The aim of this multicentre study was to evaluate the clinical significance of fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in differentiated thyroid carcinoma and to compare the results with both iodine-131 whole-body scintigraphy (WBS) and technetium-99m 2-methoxyisobutylisonitrile (MIBI) or thallium-201 chloride (Tl) scintigraphy. Whole-body PET imaging using FDG was performed in 222 patients: 134 with papillary tumours, 80 with follicular tumours and 8 with mixed-cell type tumours. Finally, for each case an overall clinical evaluation was done including histology, cytology, thyroglobulin level, ultrasonography, computed tomography and subsequent clinical course, to allow a comparison with functional imaging results. Sensitivity of FDG-PET was 75% and 85% for the whole patient group (n = 222) and the group with negative radioiodine scan (n = 166), respectively. Specificity was 90% in the whole patient group. Sensitivity and specificity of WBS were 50% and 99%, respectively. When the results of FDG-PET and WBS were considered in combination, tumour tissue was missed in only 7%. Sensitivity and specificity of MIBI/Tl were 53% and 92%, respectively (n = 117). We conclude that FDG-PET is a sensitive method in the follow-up of thyroid cancer which should be considered in all patients suffering from differentiated thyroid cancer with suspected recurrence and/or metastases, and particularly in those with elevated thyroglobulin values and negative WBS.

Primary choriocarcinoma of the pulmonary artery mimicking pulmonary embolism.

Due to their rarity, primary tumours of the pulmonary arteries are often incorrectly diagnosed as more common diseases such as pulmonary thromboembolism and are seldom diagnosed during a patient's lifetime. Surgery or potentially curative chemotherapy may therefore be withheld. We report a patient with a primary choriocarcinoma of the left pulmonary artery, which was first suspected on a CT scan. The neoplastic nature of the obstruction of the pulmonary arteries was confirmed by positron emission tomography.

Fluorine-18-FDG and iodine-131-iodide uptake in thyroid cancer.

UNLABELLED: We conducted a prospective study to define the sensitivity of 131I scintigraphy and 18FDG PET whole-body scanning in the detection of thyroid cancer and metastases. METHODS: Forty-one patients with differentiated thyroid carcinoma who underwent thyroidectomy and 131I elimination of the remaining thyroid were studied by 18FDG whole-body PET in 52 examinations and by 131I whole-body scanning. RESULTS: Combined 18FDG and 131I imaging resulted in a sensitivity of about 95%, with alternating uptake of 131I and 18FDG in the metastases: 131I trapping metastases with no 18FDG uptake and 18FDG trapping metastases with no 131I uptake. Five uptake types were differentiated. Alternating uptake was found in about 90% of the patients, which was nearly identical to the sensitivity of the combined 131I/18FDG investigation. In six patients with increasing human thyroglobulin levels, we found that 18FDG whole-body PET localized positive neck metastases of papillary thyroid carcinomas that were histologically confirmed after extirpation. CONCLUSION: Combination 18FDG and 131I whole-body imaging protocol enables detection of local recurrence or metastases on whole-body scans that are often not shown by other imaging methods. Biochemical grading of thyroid cancer may also be possible with this method: Tumors with remaining functional differentiation for hormone synthesis and iodine uptake have low glucose metabolism in more than 95%; tumors without this functional differentiation of 131I uptake show high, glucose metabolism. Fluorine-18-FDG uptake seems to be an indicator of poor functional differentiation, and possibly higher malignancy, in thyroid cancer.

Positron emission tomography helps to diagnose tumor emboli and residual disease in choriocarcinoma.

BACKGROUND: Positron emission tomography (PET) has been shown capable of identifying malignant tissues. PATIENTS AND METHODS: WB-PET imaging in two women with metastatic choriocarcinoma is described. RESULTS: In a woman with tumor emboli secondary to a choriocarcinoma, WB-PET was the only noninvasive investigation to differentiate between tumor and blood clots. Moreover, PET helped to localize residual tumor tissue in another woman with persisting high beta-HCG serum levels after chemotherapy. CONCLUSIONS: WB-PET helps to localize tumor tissue in patients suffering from choriocarcinoma.

Catecholamine secreting glomus tumor detected by iodine-123-MIBG scintigraphy.

We report the case of a 41-yr-old woman who presented with arterial hypertension and tinnitus in the right ear synchronous with pulse. She had previously undergone surgery for suspected pheochromocytoma without positive therapeutic effect. CT and MRI revealed a homogenous tumor with contrast enhancement in the right hypotympanon and foramen jugulare, and [123I]metaiodobenzylguanidine (MIBG) scintigraphy demonstrated strong tracer uptake in the same area. Selective venous sampling of catecholamines in the ipsilateral jugular vein confirmed the tumor to have originated from hormone production.

Positron emission tomography and ultrasonography. A comparative retrospective study assessing the diagnostic validity in lymph node metastases of malignant melanoma.

BACKGROUND AND DESIGN: A retrospective study involving 20 patients with melanoma with clinically suspicious lymph nodes was conducted to compare the diagnostic validity of fludeoxyglucose F 18 positron emission tomography (PET) and real-time ultrasonography in lymph node metastases of malignant melanoma. RESULTS: A total of 83 lymph nodes were assessed with ultrasonography and PET. Imaging results were confirmed by histologic studies or close follow-up ultrasonographic examinations. Positron emission tomography revealed a sensitivity of 74% and a specificity of 93%. Both investigative methods show comparative sensitivity and specificity. CONCLUSIONS: Ultrasonography is much easier to perform, less time-consuming, and less expensive than PET and it is nonhazardous; therefore, it is ideal for follow-up procedures. Since in routine staging procedures, only sites of expected lymph node involvement are examined, there is a risk of metastases being missed in cases of atypical drainage patterns. Fludeoxyglucose F 18 PET can image proliferating tumors in multiple organ systems and lymph node sites in one session, making it suitable for screening in primary staging procedures and for monitoring response to therapy. Since it is based on metabolic changes, there is good differentiation between scar and tumor tissue. Major disadvantages are restricted access to investigation centers, high imaging costs, and limited anatomical location of metastatic lesions. We conclude that PET does not offer significant advantages in the diagnosis of lymph node metastases compared with ultrasonography.

[18FDG whole-body PET in differentiated thyroid carcinoma. Flipflop in uptake patterns of 18FDG and 131I]. / 18FDG-Ganzkörper-PET bei differenzierten Schilddrüsenkarzinomen. Flipflop im Speichermuster von 18FDG und 131J.

In 27 examinations of 24 patients with differentiated thyroid carcinoma an alternating pattern of metastases with either 131I- or FDG-uptake was found. In the follow-up of these patients this flip-flop pattern was seen in 89% (17/19) of patients with metastases and uptake of 131I or FDG as described here as uptake types 1 and 2 (type 1: FDG-positive and 131I-negative; type 2: FDG-negative and 131I-positive). In 4 patients a mixed type was observed (uptake type 3), i.e. a combination of metastases with uptake types 1 and 2 in the same patient. Metastases of papillary or follicular thyroid carcinoma without uptake of iodine have all been found to be FDG-positive in patients with an increase of thyroglobulin and with negative diagnostic results from other imaging modalities, and were histologically confirmed by surgery. False-negative or false-positive cases were not observed in this study. The FDG uptake showed an inverse proportionality to iodine uptake and to tumor differentiation. Increased glucose metabolism is a sign of higher malignancy.

Incidental finding of a hepatic lesion: differential diagnostic problems for fibrolamellar hepatic carcinoma.

We report the case of a 39-yr-old female with a liver lesion that was incidentally detected by ultrasound. Examination of biopsy specimens revealed focal nodular hyperplasia. A metastatic tumor in the right os ilium developed in the following weeks and showed specific uptake of 99mTc-hepatic 2,6-dimethyliminodiacetic acid (HIDA), suggesting metastasis from a differentiated hepatocellular carcinoma. The final pathologic diagnosis was multifocal, solid and glandular hepatocellular carcinoma, partly differentiated as fibrolamellar carcinoma, and an osseous metastasis from the differentiated hepatocellular carcinoma.