John Powe

Benign causes of 18-FDG uptake on whole body imaging

C OST-EFFECTIVENESS and high accuracy of whole body 1 8-Fluorodeoxyglucose positron emission tomography (18-FDG-PET) have been established for several malignancies. 2,3 However, pitfalls have been encountered due to variable degrees of 18-FDG uptake by benign pathology. 4-66 In the majority of the cases visual interpretation (slight uptake, irregular or diffuse pattern) and quantitative analysis with different cut-off values, along with the physical examination and radiological correlation, will clarify the underlying causes. The physiological and artifactual accumulation 4,67 in 18-FDG whole body scans, and the technical and biological factors causing false-positive results 15 have been reviewed recently. We report seven cases of 1 8-FDG uptake related to lactation (Fig 1), muscle artifact at the insertion of the Latissmus Dorsi (Fig 2), esophagitis (Fig 3), a tracheostomy tube (Fig 4), ectopic pelvic kidney (Fig 5), hydatid cyst (Fig 6), and chronic nonspecific lymphadenitis (sinus histiocytosis) (Fig 7). The following are the reported benign causes of 1 8-FDG uptake that should be considered in interpreting whole body scans to decrease the rate of false-positive results in oncologic patients.

F-18 fluorodeoxyglucose chest uptake in lung inflammation and infection.

PURPOSE F-18 fluorodeoxyglucose (FDG) may accumulate at sites of inflammation or infection, making interpretation of whole-body scans difficult in patients with cancer. METHODS More than 650 whole-body positron emission tomographic (PET) scans performed to examine patients with cancer were reviewed to identify uptake in pulmonary infection or inflammation based on the appearance of F-18 FDG chest uptake, chest radiographs, computed tomography, or all of these. RESULTS Ten patients had uptake in benign lung disease. Eight patients had head and neck tumors and two patients had breast cancer. Intense focal or multifocal F-18 FDG chest uptake was seen in 6 of 10 scans. This was difficult to distinguish from pulmonary metastases based on the scan appearance. However, in the remaining patients, the uptake was atypical for malignancy and displayed an apical, segmental, or lobar pattern. In all patients, the F-18 FDG lung uptake corresponded to benign radiologic changes (infiltration, consolidation, or atelectasis), and the final diagnosis was pulmonary inflammation or infection. Nine patients were asymptomatic and one patient had clinical aspiration pneumonia. Follow-up PET scans were performed in five patients to evaluate their conditions. Chest uptake disappeared completely in three patients and partially in two patients, and there were no new findings. Variable degrees of F-18 FDG chest uptake have been reported with more than 40 different benign causes. They can be classified based on the underlying mechanism into four major categories: 1) Inflammation or infection, 2) benign tumor, 3) physiologic activity, and 4) iatrogenic. Most of these false-positive cases are included in the first category. CONCLUSIONS Pulmonary infection or inflammation might predispose patients to localized F-18 FDG chest uptake mimicking pulmonary metastases and limiting the specificity of whole-body scans performed in patients with cancer.

F-18-FDG uptake in tuberculosis.

Two patients are described who showed abnormal fluorine-18 fluorodeoxyglucose (F-18 FDG) uptake that was due to benign disease, specifically tuberculous lymphadenitis and pneumonitis. The first patient had ulceration and oozing of the left nipple that was related to Pagets disease. An F-18 FDG PET, whole-body scan, which was performed for staging, showed no breast uptake. However, there was intense multifocal uptake in mediastinal, supraclavicular, and para-aortic areas that was confirmed radiologically to represent widespread lymphadenopathy. Pathologic examination of a mediastinal lymph node showed active tuberculosis. The second patient showed intense focal F-18 FDG uptake in mediastinal and supraclavicular areas and para-aortic lymphadenopathy due to non-Hodgkins lymphoma. In addition, there was abnormal F-18 FDG lung uptake that revealed the presence of acid-fast bacilli on bronchial lavage. Intense focal F-18 FDG uptake in widespread lymphadenopathy or in the lung could be caused by infectious diseases such as tuberculosis. This possibility should be considered when whole-body scans of patients with cancer are interpreted, especially in those with a high incidence of infectious disease.

F-18 FDG uptake in breast infection and inflammation.

PURPOSE Whole-body fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET) scanning has been useful in the management of breast cancer. However, F-18 FDG uptake sometimes has been associated with benign breast disease. Four cases are reported of F-18 FDG breast uptake caused by infectious or inflammatory mastitis that mimics malignant disease. METHODS AND RESULTS Two women had F-18 FDG whole-body scans for the evaluation of a large breast mass after inconclusive results of ultrasonography. In both cases, intense focal F-18 FDG breast uptake was noted that mimicked breast cancer. Histologic examination showed, in one patient, chronic granulomatous infiltration that likely represented tuberculous mastitis, because she showed a good clinical response to empirical anti-tuberculous treatment. The second patient had lactational changes associated with acute inflammation, and the culture grew Staphylococcus aureus. The breast mass completely disappeared 3 weeks after a course of antibiotic treatment. The other two patients had staging F-18 FDG PET scans 1 and 12 months after lumpectomy for breast carcinoma to detect residual, recurrent, or metastatic disease. Both scans showed a ring-like uptake in the involved breast, with superimposed intense focal uptake suggesting tumor necrosis centrally and malignant foci peripherally. In both cases, histologic examination revealed hemorrhagic inflammation secondary to postsurgical hematomas and no evidence of malignancy. CONCLUSION Acute or chronic infectious mastitis and postsurgical hemorrhagic inflammatory mastitis should be considered in patients who have a breast mass, especially those with a history of tenderness or surgery.

False-positive radioiodine uptake in the abdomen and the pelvis: radioiodine retention in the kidneys and review of the literature.

Because the kidneys are usually not visualized on radioiodine whole-body scans, the renal uptake can be mistaken for a thyroid cancer metastasis. The authors report the prevalence and characteristics of radioiodine retention in the kidneys and review the reported causes of false-positive radioiodine uptake in the abdomen and pelvic areas. Radioiodine uptake in the renal bed was noted on 9 of 400 (2.2%) I-123 diagnostic whole-body scans performed over a 7-month period in our center. The uptake was noted more clearly on posterior views, cleared on delayed images after further hydration, and was not consistently present on follow-up scans. It was unilateral and mimicked a renal or adrenal metastasis in 44% of the scans. In three cases, the uptake was associated with a dilated calyx, an extrarenal pelvis, or a voluminous pelvis. False-positive radioiodine uptake in the abdomen and pelvis has been previously reported in association with 14 different conditions. However, renal retention may represent the most common cause of false-positive radioiodine uptake in the abdomen pelvis. Delayed imaging after additional hydration is usually sufficient to clarify its origin.

F-18 FDG uptake in benign esophageal disease.

We describe three patients who had obstructive esophageal symptoms and conventional radiologic examinations strongly suggesting the presence of esophageal cancer. Whole-body PET scans showed variable degrees of F-18 fluorodeoxyglucose (FDG) uptake in the involved esophagus that supported this diagnosis. In two patients, additional intense focal uptake was apparent in the hilum, mediastinum, and the supraclavicular area, consistent with lymph node metastases. One patient had intense F-18 FDG linear uptake secondary to bacterial esophagitis in an esophageal stricture that cleared after a course of antibiotic treatment. The second patient had moderate uptake in association with a stricture in the lower one third of the esophagus that was histologically proved to be Barrett’s esophagus. The third patient had mild uptake related to esophageal spasm and gastroesophageal reflux.

Radioiodine uptake in inactive pulmonary tuberculosis

Abstract. Radioiodine may accumulate at sites of inflammation or infection. We have seen such accumulation in six thyroid cancer patients with a history of previously treated pulmonary tuberculosis. We also review the causes of false-positive radioiodine uptake in lung infection/inflammation. Eight foci of radioiodine uptake were seen on six iodine-123 diagnostic scans. In three foci, the uptake was focal and indistinguishable from thyroid cancer pulmonary metastases from thyroid cancer. In the remaining foci, the uptake appeared nonsegmental, linear or lobar, suggesting a false-positive finding. The uptake was unchanged, variable in appearance or non-persistent on follow-up scans and less extensive than the fibrocystic changes seen on chest radiographs. In the two patients studied, thyroid hormone level did not affect the radioiodine lung uptake and there was congruent gallium-67 uptake. None of the patients had any evidence of thyroid cancer recurrence or of reactivation of tuberculosis and only two patients had chronic intermittent chest symptoms. Severe bronchiectasis, active tuberculosis, acute bronchitis, respiratory bronchiolitis, rheumatoid arthritis-associated lung disease and fungal infection such as Allescheria boydii and aspergillosis can lead to different patterns of radioiodine chest uptake mimicking pulmonary metastases. Pulmonary scarring secondary to tuberculosis may predispose to localized radioiodine accumulation even in the absence of clinically evident active infection. False-positive radioiodine uptake due to pulmonary infection/inflammation should be considered in thyroid cancer patients prior to the diagnosis of pulmonary metastases.

18Fluoro-2-deoxyglucose (18FDG) PET scan of the brain in glutaric aciduria type 1 : clinical and MRI correlations

The clinical, PET (positron emission tomography) and MRI (magnetic resonance imaging) findings of brain studies in eight patients, previously diagnosed to have glutaric aciduria type 1, were retrospectively reviewed. The neurological findings typically consisted of variable degrees of dementia and extrapyramidal symptoms (dystonia, choreoathetosis and rigidity). Both MRI and PET showed involvement of the putamina in all the patients. The PET scan demonstrated lesions in the head of the caudate nuclei in all of the patients. Brain atrophy, and in particular the characteristically-enlarged Sylvian fissures, was better demonstrated by MRI. On the other hand, the cerebral cortex and thalamic structures were found to be normal by MRI in all patients, whereas PET scan showed decreased uptake in the cerebral cortex in seven, and in the thalami in three patients. Correlation between imaging and clinical findings was found to be good when both PET scan and MRI findings of the brain were taken into consideration. Therefore, the functional (PET) and structural (MRI) studies of the brain were complementary in the imaging evaluation of glutaric aciduria type 1.

Incidental second primary in the breast detected by F-18 FDG positron emission tomography scan.

A 39-year-old women had multiple lung lesions on a follow-up chest radiograph after laparotomy and left cystectomy for an immature ovarian teratoma. Results of a work-up for metastases were normal, including beta human chorionic gonadotrophin and alpha-fetoprotein levels. An F-18 FDG positron emission tomographic (PET) whole-body scan performed to evaluate the possibility of pulmonary metastases showed no abnormality in the chest or pelvis. There was intense focal uptake in the left breast, however, suggesting an incidental second malignancy. Pathologic evaluation of the left breast mass showed infiltrating ductal cell carcinoma, for which she received chemotherapy. Histologic examination of the lung lesions showed a benign mature teratoma in one nodule and fibrosis in several of the others. In a patient with a neoplasm, F-18 FDG uptake on a whole-body scan may be unrelated to the primary tumor and could represent an incidental second malignancy.

Clinical and cerebral fdg pet scan in a patient with krabbe’s disease

A 2-year, 6-month-old Saudi male with infantile Krabbes disease was studied with fluorine-18-labeled-2-fluoro-2-deoxyglucose positron emission tomography (FDG PET) scan. The patient presented with a gradual loss of developmental milestones, irritability, and crying. At the advanced stage of the disease, he developed tonic-clonic seizures and became a microcephalic, extremely irritable, blind, spastic quadriplegic child, with no deep tendon reflexes. Laboratory studies revealed normal blood chemistry, muscle enzymes, very long chain fatty acids, and acylcarnitines. No abnormal urinary organic acids were detected. The cerebrospinal fluid protein concentration was increased. Magnetic resonance imaging of the brain revealed mild brain atrophy and white matter disease mainly in the centrum semiovale. Electroretinography was normal; however, electroencephalography and visual-evoked potentials were abnormal. Peripheral nerve conduction studies documented a demyelinating neuropathic process. The FDG PET study of the brain demonstrated a marked decrease in the metabolism of the left cerebral cortex and no uptake in the caudate heads. Normal glucose uptake was observed in the thalami, lentiform nuclei, and cerebellum. The patient did not present for subsequent clinic visits and is presumed dead.