Hypermetabolic change as a possible predictive sign of a relapsed central nervous system lymphoma

PURPOSE: A patient with abdominal lymphoma who had been in complete remission for 6 years presented with a 1-month history of dysarthria. The aim of our report is to discuss the discordance of the patient's results between magnetic resonance (MR) imaging and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET). MATERIALS AND METHODS: After the onset, FDG PET and brain MR imaging were performed. The FDG PET study included whole-body and brain scan. The MR study included pre- and postcontrast T1, T2, fluid-attenuated inversion recovery and diffusion-weighted sequences. RESULTS: Brain MR imaging showed a localized abnormal signal around the left Sylvian fissure in any sequence, although a postcontrast study exhibited poor enhancement in the lesion. Brain PET showed a widespread area of slightly increased uptake in the brain on the left side, which was quite inconsistent with the MR results. After 4 months, follow-up MR imaging revealed a widespread abnormal signal, with enhancing masses, in the hypermetabolic region. CONCLUSIONS: Hypermetabolic changes on FDG PET preceded signal changes on MR imaging, potentially suggesting that hypermetabolism occurred in the microscopic infiltration of lymphoma cells.     

Cerebral Toxoplasmosis in a Patient with AIDS on F-18 FDG PET/CT

The distinction between primary central nervous system (CNS) lymphoma and nonmalignant lesions due to opportunistic infections, in particular cerebral toxoplasmosis, is important because of the different treatments involved. A 32-year-old patient with AIDS was hospitalized for intermittent headaches. Brain magnetic resonance imaging (MRI) showed a small well-enhanced nodular lesion in the right frontal lobe. A fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET)/computed tomography (CT) scan showed moderate FDG uptake in the nodular lesion of the right frontal lobe. We present a case of cerebral toxoplasmosis in a patient with acquired immunodeficiency syndrome (AIDS) and the usefulness of F-18 FDG PET/CT in the differential diagnosis of the cerebral toxoplasmosis will be discussed.     

Solitary plasmacytoma of bone: an unusual cause of severe sacral pain in a young man

A 35-year-old man presented with insidious onset of severe sacral pain. Plain radiography, computed tomography, and magnetic resonance imaging revealed a large, locally invasive mass within the sacrum. Skeletal scintigraphy showed marked hyperemia and minimal peripheral osteoblastic activity of the sacral mass. An F-18 FDG PET study was performed for further assessment and clinical staging. The mass demonstrated high glucose avidity consistent with a high-grade tumor. Histologic examination confirmed the lesion to be a plasmacytoma. Solitary plasmacytoma of bone occurs predominantly in older patients involving the axial skeleton. This case is interesting in view of the large dimension, sacral involvement, the young age of the patient, and the appearance of this lesion across multiple imaging modalities.     

The use of whole-body fluorine-18-fluorodeoxyglucose positron emission tomography integrated with computed tomography for accurate staging and surveillance in the case of mucosa-associated lymphoid tissue

We present the case of a 79-year-old male, who was initially treated for mucosa-associated lymphoid tissue lymphoma (MALT lymphoma) of the right eyelid, and later for disease relapse in the stomach. During follow up, he was noted to have developed left arm nodules just medial to the proximal biceps muscle, which were found to be multiply enlarged lymph nodes on subsequent ultrasound imaging. Excisional biopsy of these nodes revealed MALT lymphoma. He was initially referred for consideration of radiation, but a restaging F-18 fluorodeoxyglucose positron emission tomography integrated with computed tomography (F-18 FDG PET/CT) further identified a focus of suspicious uptake in left calf, which was later also biopsy proven to be MALT lymphoma. His disease was upstaged as the result of this later finding, and the overall recommendation for treatment changed to favor systemic treatment with Rituximab.     

Diagnosing active inflammation in the SAPHO syndrome using <Superscript>18</Superscript>FDG-PET/CT in suspected metastatic vertebral bone tumors

The vertebral spine is frequently affected by the SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) syndrome. We report the collective imaging findings of hybrid F-18 fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸FDG-PET/CT), as well as bone scans and magnetic resonance imaging, in a patient who had suspected metastatic vertebral bone tumors. ¹⁸FDG-PET/CT can be utilized to exclude metastatic vertebral tumors, as well as identifying stable lesions, by demonstrating active inflammatory lesions with accurate anatomic localization through the convergence of the functional information from ¹⁸FDG uptake with the anatomic information of CT.     

Radiologic concepts of lymphoma of bone

The imaging of lymphoma of bone is illustrated by conventional radiology, computed tomography, magnetic resonance imaging, and nuclear radiology. The features of non-Hodgkin's lymphoma are demonstrated.     

Focal nodular hyperplasia (FNH): a potential cause of false-positive positron emission tomography

Positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG) has been proven to be a useful tool in the differential diagnosis of liver tumors. Focal nodular hyperplasia (FNH) is an uncommon benign liver lesion, which can be difficult to differentiate from other benign and malignant liver pathologies. FDG PET imaging usually shows uptake similar or even decreased compared to that of the normal liver. We describe a hypermetabolic FNH lesion in a patient with a history of breast cancer. Computed tomography scan, ultrasonography (US), and magnetic resonance imaging were negative. The lesion was resected, and histologic findings were consistent with FNH.     

FDG PET/CT flip flop phenomenon in treated lymphoma of bone

A 47-year-old man with primary large B-cell lymphoma of bone underwent an F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) scan for staging. The study demonstrated multiple areas of uptake consistent with osseous lymphoma. After multiple cycles of chemotherapy, a follow-up study demonstrated a dramatic flip flop appearance in which the previously noted areas of osseous lymphoma were photopenic and normal marrow appeared to have increased activity. This flip flop appearance could incorrectly suggest lymphomatous infiltration of normal marrow.     

Pituitary adenoma detected on FDG positron emission tomography in a patient with mucosa-associated lymphoid tissue lymphoma

A 52-year-old woman with a history of treated non-Hodgkin's lymphoma, B-cell type, was examined for a right eyelid mass proved on excision to be a mucosa-associated lymphoid tissue lymphoma. She was referred for F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging of the whole body, including the brain, to identify the possible presence or recurrence of lymphoma. The FDG-PET images revealed focal marked FDG uptake in the pituitary gland but no evidence of abnormal metabolic sites in the rest of the body, including the orbital regions. Magnetic resonance imaging and computed tomography confirmed a 1.8 x 1.5 cm intrasellar mass. Surgery was performed, and histologic examination revealed a nonfunctional adenoma that was negative for leukocyte common antigen staining, an antigen that is positive in lymphoma but negative in pituitary adenoma. This case provides evidence for avid uptake of FDG on PET imaging of pituitary adenomas.     

MRI diagnosis of brown tumor based on magnetic susceptibility

A 56-year-old male with chronic renal failure was incidentally found to have lytic bone lesions in the pubic symphysis, left femoral head, left acetabulum, left iliac bone, and L1 vertebra on computed tomography (CT). Subsequent magnetic resonance imaging (MRI) of the abdomen was performed (for evaluation of a renal lesion) which demonstrated marked loss of signal intensity in the L1 bone lesion on increasing TE gradient echo images, consistent with magnetic susceptibility effect due to hemosiderin. Brown tumor was confirmed at biopsy. The susceptibility imaging probes one particular histological characteristic of tissues and allows a restricted differential of lytic tumors that contain significant hemosiderin, including brown tumor.     

Musculoskeletal system

Diagnostic imaging has played a major role in the evaluation of patients with cancers of the bone and soft tissue. The imaging modalities have included radiography, computed tomography, magnetic resonance imaging, and bone scintigraphy. Current experience suggests that functional imaging with positron emission tomography (PET) and [F-18]fluorodeoxyglucose (FDG) may also have an important role in the imaging evaluation of patients with bone and soft tissue sarcoma, including guiding biopsy, detecting local recurrence in amputation stumps, detecting metastatic disease, predicting and monitoring response to therapy, and assessing for prognosis. Prospective studies with large patient groups will be essential to define the exact diagnostic role of FDG PET in this clinical setting, which should also include an evaluation of the cost-effectiveness and the short-term and long-term benefits in clinical decision making and management. In this article, we review the diagnostic utility of dedicated PET and PET combined with computed tomography imaging system in the evaluation of patients with bone and soft tissue malignancies.     

Nonossifying fibroma can mimic residual lymphoma in FDG PET: additional value of combined PET/CT

A 12-year-old girl was diagnosed with Hodgkin's lymphoma and underwent conventional cross-sectional imaging for initial staging. Chemotherapy was given according to standard pediatric protocols. At the end of therapy, an F-18 FDG PET/CT examination was performed to evaluate the therapeutic response. The scan demonstrated focal uptake of FDG in the right distal femur and residual lymphoma was taken into consideration. However, findings in the coregistered CT scan were consistent with nonossfiying fibroma, a common benign skeletal lesion. Combined PET/CT imaging can be helpful to identify benign bone lesions mimicking metastatic or residual disease in F-18 FDG PET as illustrated by this case.     

Dichotomy between Tc-99m MDP bone scan and fluorine-18 fluorodeoxyglucose coincidence detection positron emission tomography in patients with non-Hodgkin's lymphoma

The authors report two cases of non-Hodgkin's lymphoma that were evaluated not only by conventional staging work-up but also additional Tc-99m MDP bone scans and fluorine-18 fluorodeoxyglucose (F-18 FDG) coincidence detection (CoDe) positron emission tomographic (PET) imaging. There were discordant results between the Tc-99m MDP bone scans and F-18 FDG CoDe PET. In the first case, the bone marrow biopsy was positive, and F-18 FDG CoDe PET was consistent with a malignancy, but the findings of the Tc-99m MDP bone scintiscan were negative. In the second case, the bone marrow biopsy was negative, but F-18 FDG CoDe PET revealed focal skeletal involvement, which improved markedly on the follow-up study after chemotherapy. If skeletal involvement has a focal distribution and is confined to the marrow cavity, both bone marrow biopsy and bone scintigraphy can be falsely negative. In this situation, F-18 FDG PET is useful and revealing.     

F-18 fluorodeoxyglucose positron-emission tomography in the diagnosis of tumor recurrence and metastases in the follow-up of patients with breast carcinoma: a comparison to conventional imaging

AIM: To evaluate the role of F-18-fluorodeoxyglucose positron-emission tomography (F-18 FDG PET) in the follow-up of breast carcinoma in case of clinical suspicion of local recurrence or distant metastases and/or tumor marker increase in correlation to conventional imaging. MATERIAL AND METHODS: Retrospective analysis of the results of F-18 FDG PET (ECAT ART(R), Siemens CTI MS) of 62 patients (age 58.5 +/- 12.8) with surgically resected breast carcinoma (time interval after surgery, 86 +/- 82 months, mean follow-up 24 +/- 12.6 months). Patient- and lesion-based comparison with conventional imaging (CI) including mammography (MG), ultrasonography (US), computerized tomography (CT), magnetic resonance imaging (MRI), radiography (XR) and bone scintigraphy (BS). Furthermore, we evaluated the influence on tumor stage and therapeutic strategy. A visual qualitative evaluation of lesions was performed. RESULTS: On a patient base, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy for detecting local recurrence or distant metastases were calculated to be 97%, 82%, 87%, 96% and 90% compared with 84%, 60%, 73%, 75% and 74% with CI. On a lesion base, significantly more lymph node (84 vs. 23, P < 0.05) and fewer bone metastases (61 vs. 97, P < 0.05) could be detected by using F-18 FDG PET compared with CI. Sclerotic bone lesions were predominantly detected by BS. On the other hand, there were several patients with more FDG positive bone lesions and also mixed FDG positive/Tc-99m methylenediphosphonate (MDP) negative and FDG negative/Tc-99m MDP positive metastases. In case of normal tumor markers, sensitivity, specificity, PPV, NPV and accuracy for detecting local recurrence or distant metastases were calculated to be 100%, 85.0%, 78.6%, 100% and 90.3% for FDG PET and 80%, 50%, 50%, 80% and 61.5% for CI. An upstaging could be observed in 9.7% (6/62) and downstaging in 12.9% (8/62), leading to a change in therapeutic regimen in 13 patients (21%). CONCLUSIONS: F-18 FDG PET demonstrates apparent advantages in the diagnosis of metastases in patients with breast carcinoma, compared with conventional imaging on a patient base. On a lesion base, significantly more lymph node and less bone metastases can be detected by using F-18 FDG PET compared with conventional imaging, including bone scintigraphy. In patients with clinical suspicion but negative tumor marker profile, too, F-18 FDG PET seems to be a reliable imaging tool for detection of tumor recurrence or metastases. Considering the high predictive value of F-18 FDG PET, tumor stage and therapeutic strategy will be reconsidered in several patients.     

High F-18 fluorodeoxyglucose accumulation in solid pseudo-papillary tumors of the pancreas

We report two cases of young women with a solid pseudo-papillary tumor of the pancreas which having cystic and hemorrhagic components with marked calcification on computed tomography and magnetic resonance imaging. F-18 fluorodeoxyglucose positron emission tomography revealed abnormally increased accumulation of F- 18 fluorodeoxyglucose in the pancreas tail tumors, especially in the non-calcified solid portion of the tumors. These patients underwent elective resection of the masses and distal pancreatectomy and were diagnosed with solid pseudo-papillary tumors by histopathological analysis. There was no evidence of distant metastasis on follow-up after surgery and they showed no histopathological findings suggesting malignancy. These cases suggest that solid pseudo-papillary tumor may show high uptake of F-18 fluorodeoxyglucose.     

Incidental detection of Sertoli–Leydig cell tumor by FDG PET/CT imaging in a patient with androgen insensitivity syndrome

A 29-year-old female patient who was being followed up for differentiated papillary thyroid carcinoma was referred to us for exploration of any possible metastasis since her serum thyroglobulin levels were high. The patient underwent an F-18 fluorodeoxyglucose positron emission tomography study, and a pathologically increased FDG uptake at the left lower abdomen was detected corresponding to a solid, cystic lesion on CT images. The patient had a history of primary amenorrhea and, together with the magnetic resonance imaging findings of absent uterus, short and blind end vagina, a diagnosis of androgen insensitivity syndrome was made. The patient underwent laparoscopic left pelvic mass resection, and the histopathology of the lesion revealed Sertoli–Leydig cell tumor.     

FDG-PET on the trail of an unsuspected primary malignancy in the breast

Proper identification of the primary malignancy can radically alter clinical management for the patient's benefit. This is a report of an unsuspected primary breast cancer in a patient being worked up for presumptive lymphoma. Prior investigation of lymphedema in the left lower extremity found widespread lymphadenopathy on computed tomography imaging, leading to initial biopsy revealing adenocarcinoma of unknown primary. F-18 fluorodeoxyglucose PET/computed tomography altered management by localizing an F-18 fluorodeoxyglucose avid breast nodule, directing breast biopsy with specific immunohistochemical analysis for breast cancer lineage in metastatic adenocarcinoma. The patient responded well to breast cancer-targeted chemotherapy.     

FDG PET for giant cavernous hemangioma: important clue to differentiate from a malignant vascular tumor in the liver

Giant cavernous hemangioma of the liver sometimes has a very inhomogeneous appearance with intratumoral degeneration on computed tomography or magnetic resonance imaging, and may mimic a malignant hepatic tumor, including angiosarcoma. There are many reports about F-18 fluorodeoxyglucose (FDG) uptake of angiosarcoma; however, knowledge regarding positron emission tomography findings with FDG for giant hepatic cavernous hemangioma is still limited. We herein present 2 cases of giant hepatic cavernous hemangioma in which low FDG uptake was considered helpful to differentiate from malignant hepatic tumor.     

Fortuitous detection of papillary carcinoma of the thyroid with F-18 FDG positron emission tomography in a patient with non-Hodgkin lymphoma

Use of F-18 fluorodeoxyglucose positron emission tomography (F-18 FDG PET) in patients with known thyroid cancer is well documented, but the role of this imaging modality in the initial workup of a thyroid nodule has not been defined. The incidental finding of a hypermetabolic focus in the thyroid on F-18 FDG PET in patients with a variety of primary malignancies is reported. Based on the authors' literature search, this is the first documented case of a thyroid cancer resulting from papillary carcinoma detected in a patient with a history of non-Hodgkin lymphoma.     

B cell lymphoma: a case with localized involvement of the prostate on F-18-FDG examination

An 80-year-old man had symptoms of urinary retention. Biopsy of the prostate revealed B cell lymphoma. To evaluate the extent of the disease, an F-18 FDG study was performed with positron emission tomography/computed tomography (CT). One hour after intravenous administration of 18.5 mCi F-18 FDG, imaging was carried out from the skull base to the upper thigh. An area of moderately increased activity was noted within the prostate bed. A noncontrast CT, for attenuation correction and anatomic localization, revealed maintenance of fat planes around the prostate, indicating disease localized to that organ. Hence, a B cell lymphoma had been localized to the prostate.