FDG PET evaluation of residual masses and regrowth of abdominal lymph node metastases from colon cancer compared with CT during chemotherapy.

Fluorine-18-2-deoxy-2-fluoro-D-glucose (F-18 FDG) PET may be more suitable for follow-up after cancer treatment than other morphologic approaches, because it reflects tumor viability. A patient with abdominal lymph node metastases from colon cancer was followed by CT and F-18 FDG PET during chemotherapy. F-18 FDG PET tumor images changed in accordance with the clinical progress, whereas CT findings were relatively unchanged. This case clearly shows the utility of F-18 FDG PET for follow-up during cancer chemotherapy.     

Primary peripheral T-cell lymphoma of the colon mimics inflammatory bowel disease: a potential pitfall with F-18 FDG PET/CT imaging

We present a case of a woman with ulcerative colitis who was referred for an F-18 FDG PET/CT after a suspicious colonoscopy and biopsy. PET/CT showed multiple elongated foci of intense FDG uptake in the colon, a pattern commonly reported with inflammatory bowel disease; however, the possibility of lymphoma was raised. Reevaluation of the biopsies with immunohistochemistry and molecular studies revealed a peripheral T-cell lymphoma and the patient was treated with a total colectomy. In this case, F-18 FDG PET/CT was very useful in determining the extent of the disease. This case also highlights a potential pitfall whereby the tubular and multifocal appearance of this lymphoma subtype can mimic the appearance of bowel involved by inflammatory bowel disease especially on novel techniques such as PET/CT enterography and PET/CT colonography.     

Systemic tuberculosis presenting as an epiglottic mass detected on F-18 FDG PET/CT

A 32-year-old man presented with asthenia, weight loss, cough, and dysphagia following a recent stay in Morocco. Endoscopy showed a bulky mass of the epiglottis suspected of being a malignant tumor. The patient underwent jointly an F-18 FDG PET/CT and a biopsy of the tumor. Against all expectations, biopsy revealed granulomatous inflammation with epitheloid giant cells and caeseating necrosis. These findings associated with the presence of acid-fast bacilli in the sputum smears were highly suggestive of laryngeal tuberculosis, which was confirmed later after cultivation of mycobacteria. F-18 FDG PET showed diffuse pharyngolaryngeal and lung uptake with bilateral cervical and abdominal nodes, but also one thoracic vertebral uptake. Lung CT could have revealed carcinomatous dissemination, but cavitary lesions in some pulmonary segments were more evocative of tuberculosis. Moreover, cerebral MRI showed brain tuberculomas not visualized on F-18 FDG PET/CT. The patient was treated with a 5-antituberculosis drug regimen, which improved clinical symptoms with epiglottis mass regression, and lung CT image reduction, clinching the systemic tuberculosis diagnosis. A control F-18 FDG PET/CT performed 5 months later showed disappearance of the pharyngolaryngeal and node uptake, with an improvement of lung uptake without normalization, arguing for persistent disease. Unexpected pathologic findings may be present in more than 3% of neck dissections. Although this is usually indolent, with the underlying SCC remaining the main prognostic determinate, it may significantly complicate postoperative management.     

A Case of Urethral Metastasis from Sigmoid Colon Cancer Diagnostically and Prognostically Indicated by F-18 FDG PET/CT

Urethral metastasis from colorectal cancer is rare and is known to have a poor prognosis. A 72-year-old man with a history of colectomy and colostomy due to sigmoid colon cancer was admitted to the emergency room with bowel distension, rectal bleeding and urinary symptoms. Computed tomography of the abdominopelvis showed sigmoid colon cancer with multiple metastases involving the liver. Positron emission tomography with F-18 fluorodeoxyglucose (FDG) showed multiple hypermetabolic foci in the liver, penis and pubic bone, which otherwise could not be diagnosed. The lesions revealed no improvement with chemotherapy and urological surgery on follow-up F-18 FDG PET/CT. We present a case of urethral metastasis of sigmoid colon cancer diagnostically and prognostically indicated by F-18 FDG PET/CT.     

Abdominal Mesh Implant Showing FDG Uptake on PET/CT

F-18 fluorodeoxyglucose (FDG) uptake by a mesh implant might be caused by a foreign body granulomatous reaction with inflammation and fibrosis, which can be demonstrated by positron emission tomography/computed tomography (PET/CT). A 71-year-old man underwent F-18 FDG PET/CT for the follow-up evaluation after an operation for colonic adenocarcinoma. On PET/CT imaging, there was a rectangular-shaped FDG uptake (maximal standardized uptake value, maxSUV: 3.4) in the anterior abdominal wall. On the review of the medical records, the patient had a history of herniorrhapy for the reinforcement of the abdominal wall 2 months previously, using a mesh implant consisting of polytetrafluoroethylene (Teflon). We report a case of FDG uptake associated with surgical procedures including mesh implant on F-18 FDG PET/CT.     

Incidental focal F-18 FDG accumulation in lung parenchyma without abnormal CT findings

F-18 fluorodeoxyglucose (FDG) PET/CT that simultaneously offers anatomic and metabolic information is widely used and has become an effective modality in many clinical fields, especially oncology. For accurate interpretation, it is necessary to understand false-positive findings in the F-18 FDG PET image, such as physiologic conditions, findings related to patients’ medical and surgical histories, normal variants, and artificial conditions. We report three cases of incidental focal F-18 FDG accumulation in lung parenchyma without abnormal CT findings in the PET/CT images. In the primary PET/CT studies, two cases showed single and one case showed multiple FDG foci in the lung without any CT abnormalities. All FDG accumulations disappeared in PET/CT studies repeated 1–3 days after the primary scannings. These artifacts are probably related to microembolisms attributable to the intravenous injection of F-18 FDG. Therefore, a cautious interpretation of the correspondence between anatomic and metabolic images is required and repeated PET/CT is helpful.     

PET imaging of cerebral and pulmonary Nocardia infection

We report the case of a 69-year-old man who was suspected to have lung cancer with a single metastasis to the brain. Initial workup for neurologic and pulmonary symptoms demonstrated a ring-enhancing lesion in his right frontal lobe on MRI and a lung mass on CT. An F-18 fluorodeoxyglucose positron emission tomography (FDG PET) scan demonstrated marked glucose hypermetabolism in the lung and brain lesions with maximal standard uptake values (SUV) in both lesions of approximately 11. Biopsy of the brain mass revealed an abscess and cultures grew Nocardia. He was treated for nocardiosis, and a repeat CT of the chest in 2 months and MRI of the brain in 5 months showed nearly complete resolution of the lesions. Currently, there are few reported cases of PET evaluation of brain abscesses, particularly Nocardia. We discuss the appearance of brain infections on FDG PET scans in immunocompetent and immunocompromised patients.     

A case of secondary hemochromatosis with high uptake of liver in F-18 FDG PET/CT imaging

Hemochromatosis is an iron storage disorder with progressive and massive deposition of iron in the parenchymal cells of various organs. A 72-year-old woman with rheumatoid arthritis diagnosed with secondary hemochromatosis underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography(PET)/computed tomography (CT) to search for malignancy. F-18 FDG PET/CT incidentally showed homogeneous and high FDG uptake (mean SUV, 4.8) in the liver with high density. FDG uptake seemed to be reflected by the functional abnormality of liver. Hemochromatosis should be considered when making a diagnosis of homogeneous high F-18 FDG uptake in liver with high density on CT image.     

PET/CT appearance of appendiceal adenocarcinoma

Appendiceal cancer is rare and is associated with a poor prognosis because it is usually found at an advanced stage. We report the case of a 58-year-old man with appendiceal adenocarcinoma, who complained of right lower abdominal malaise for a couple of months. The tumor was detected early on contrast-enhanced computed tomography and F-18 FDG PET/CT. It appeared as an obvious enhancement and intense abnormal tracer uptake focus in front of the right psoas major, which was easily misinterpreted as an enlarged lymph node.     

Diffuse FDG uptake in acute prostatitis

Whole body bone scan and abdominal computed tomography (CT) of a 77-year-old man with intractable back pain revealed a destructive bone lesion in the lumbar spine. The F-18 FDG PET/CT scan, performed under the impression of an unknown primary cancer, showed diffusely intense FDG uptake in the enlarged prostate and mild FDG uptake in the lumbar spine. The patient had pyuria and mild fever during admission. Laboratory findings showed elevation of the serum prostate specific antigen (95.69 ng/ml). Blood culture yielded Klebsiella pneumoniae. The prostate biopsy showed acute inflammation with no malignancy and the lumbar spine biopsy showed chronic osteomyelitis.     

Cold tuberculous abscess identified by FDG PET

We report FDG PET of two cases of cold abscess due to Mycobacterium tuberculosis. Case 1 had colon cancer; FDG PET showed high FDG uptake in the colon lesion and low uptake in the inguinal lesion. The latter was a tuberculous cold abscess confirmed by CT/MRI and biopsy. Case 2 received radiotherapy for lung cancer and presented with suspected vertebral metastasis. Further studies revealed tuberculosis of the vertebra and a tuberculous cold abscess in the iliopsoas muscle. FDG PET showed moderate uptake in the third lumbar spine and low uptake in the abscess center of iliopsoas lesion. Both tuberculous cold abscesses showed moderate FDG uptake in the capsule and low uptake in the center. These features are unique compared with non-tuberculous abscess and typical tuberculosis lesions, which are characterized by high FDG uptake. Pathologically, tuberculous cold abscess is not accompanied by active inflammatory reaction. Our findings suggested that the FDG uptake by tuberculous lesion varies according to the grade of inflammatory activity. The new diagnostic features of tuberculous cold abscess may be useful in the evaluation of such lesions by FDG PET.     

Hepatic adenomatosis may mimic metastatic lesions of liver with 18F-FDG PET/CT

Hepatic adenomatosis is an uncommon benign neoplasm, with the presence of multiple adenomas (generally more than 4) within the liver. A 52-year-old woman presented with multiple (>10) solid liver lesions detected with abdominal ultrasonography and verified with magnetic resonance imaging (MRI). Subsequently, F-18 FDG PET/CT demonstrated increased uptake in these lesions. Histology revealed hepatic adenomatosis. F-18 FDG PET/CT cannot reliably differentiate hepatic adenomas from malignant processes on the basis of uptake.     

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.     

Solitary splenic metastasis in a patient with a malignant melanoma diagnosed with F-18-FDG PET scanning

A 71-year-old woman with a history of stage III melanoma was hospitalized for evaluating fever of unknown origin and severe left upper quadrant abdominal pain. A computed tomography scan of the abdomen revealed a solitary lesion in the spleen, 10.5 x 10.4 x 10.1-cm, causing splenomegaly. Fused F-18 FDG PET/CT images revealed a solitary splenic metastasis and a focus of increased uptake in the region of the previously removed melanoma at the right scapula. Based on the clinical findings and CT and PET scans, malignant melanoma (stage IV) was diagnosed. Splenectomy was performed subsequently. The histopathologic finding was consistent with a metastasis of a melanoma.     

F-18 FDG PET positive hilar and mediastinal lymphadenopathy mimicking metastatic disease in a melanoma patient treated with interferon-alpha-2b

A 49-year-old man with a history of recurrent melanoma in the parotid was treated with parotidectomy, external beam radiation, and high-dose interferon-alpha-2b. Combined F-18 fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) performed for restaging demonstrated multiple bilateral hilar and mediastinal hypermetabolic foci corresponding to hilar and mediastinal lymphadenopathy. Cytologic specimens obtained by bronchoscopy were negative for malignancy, revealing reactive lymph nodes. Subsequent FDG PET/CT showed regression of the findings. Awareness of possible interferon-associated reaction in melanoma patients who undergo FDG PET is important to avoid pitfalls in the interpretation.     

Malignant epithelioid hemangioendothelioma of the lower extremity: staging with F-18 FDG PET/CT

A 36-year-old woman presented with a 5-month history of a growing left thigh mass, causing difficulty walking. Biopsy revealed a malignant epithelioid hemangioendothelioma (EHE), and the patient was referred for a staging F-18 FDG PET/CT that showed intense FDG uptake in the thigh mass, but no FDG-avid local lymph nodes or distant metastases. A few reports have noted the usefulness of F-18 FDG PET/CT imaging in the staging of EHEs in the lung, liver, and bone marrow. This rare study highlights the usefulness of F-18 FDG PET/CT in the staging of malignant EHE of the soft tissues of the extremities.     

Palpation thyroiditis seen on F-18 FDG PET/CT

A 29-year-old woman presented with a new right supraclavicular mass on a background of resection of a malignant melanoma from her right shoulder before 4 years. F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) imaging revealed uptake in a right supraclavicular node and the inferior pole of the left lobe of the thyroid gland. Subsequent resection and histology of the right supraclavicular node and the left lobe of the thyroid gland demonstrated metastatic melanoma and palpation thyroiditis, respectively. A number of malignant and benign pathologies of the thyroid demonstrate FDG uptake, with 75% being benign. To our knowledge, the findings of palpation thyroiditis on FDG PET/CT have never been previously described.     

Acute varicella infection mimics recurrent Hodgkin's disease on F-18 FDG PET/CT

We report a case where acute varicella infection, chickenpox, mimics the findings of recurrent Hodgkin disease on F-18 FDG PET/CT. A 28-year-old man with a history of Hodgkin disease in remission had fatigue, pyrexia, and a raised ESR. His F-18 FDG PET/CT, performed to exclude lymphoma recurrence, demonstrated FDG-avid lymphadenopathy and increased FDG uptake in his spleen. A day later he developed the generalized rash of acute varicella infection. This was managed with valacyclovir. Repeat F-18 FDG PET/CT done 1 month later showed no evidence of FDG-avid disease. In this patient the stimulation of an immune response by the acute viral infection mimics recurrent lymphoma.     

F-18 FDG PET demonstration of a thyroid metastasis in a patient with colon cancer

A 51-year-old man with a history of surgical removal of sigmoid colon cancer underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) to search for distant metastases and/or local recurrence because the carcinoembryonic antigen level was elevated. F-18 FDG PET images showed increased focal FDG uptake in the left lobe of the thyroid. Computed tomography images showed thyroid tumor in the left lobe as well as F-18 FDG PET images. Thereafter he underwent thyroidectomy and the resected specimen was histopathlogically shown to have thyroid metastasis from colon cancer. F-18 FDG PET was useful to detect thyroid metastasis from colon cancer as well as the most frequently seen metastatic sites such as liver, lungs, and lymph nodes.     

Clinical role of FDG PET/CT for methotrexate-related malignant lymphoma

Methotrexate-related malignant lymphoma (MTX-RML) is a type of therapy-related lymphoma, and it often occurs in patients with rheumatoid arthritis. The most distinctive characteristic of MTX-RML is a quick response to withdrawal of MTX. However, because there is a risk of recurrence without a distinctive indicator of disease, close follow-up is needed. We present F-18 2-fluoro-2-deoxyglucose (FDG) postitron emission tomography (PET) or computed tomography (CT) images of MTX-RML along with the characteristic clinical presentation of MTX-RML. FDG PET/CT has the advantage of being able to detect malignant lymphoma in patients who have undergone MTX treatment. After withdrawal of MTX, FDG uptake decreases along with a reduction in the volume of lesions. Although recurrent lesion develops independent to the initial FDG PET/CT findings, FDG PET/CT is useful for early detection of unexpected recurrent lesions. FDG PET/CT allows for the assessment of malignant lymphoma and recurrent lesions in patients who received MTX therapy, which is crucial for the management of MTX-RML.