Elizabeth Yung

Cutaneous and subcutaneous imaging on FDG-PET: benign and malignant findings.

F-18 fluorodeoxyglucose positron emission tomography (F-18 FDG PET) has been shown to be useful in the evaluation of many tumors due to its high sensitivity and specificity. However, false-positive interpretations may occur from benign subcutaneous and cutaneous etiologies. At our institution we have encountered FDG-PET scans which demonstrated a variety of cutaneous and subcutaneous lesions including stomas, hernias, rhinophyma, dose infiltrations, physiologic muscle uptake, and tophaceous gout. Additionally, malignant cutaneous and subcutaneous malignant lesions may also demonstrate substantial F-18 FDG uptake on PET scans, including lymphoma, skin metastases, and melanoma. The purpose of this atlas article is to demonstrate and review key features of various cutaneous and subcutaneous lesions, both benign and malignant, which can result in hypermetabolism on FDG-PET or PET-CT scans.

The utility of thyroid nuclear imaging and other studies in the detection and treatment of underlying thyroid abnormalities in patients with endogenous subclinical thyrotoxicosis

PURPOSE Endogenous subclinical thyrotoxicosis is diagnosed when a patient who is not taking exogenous thyroid hormone has a suppressed level of thyroid-stimulating hormone with normal levels of the free thyroid hormones thyroxine and triiodothyronine and other known causes of a suppressed thyroid-stimulating hormone level have been excluded. Although such a condition is caused by underlying thyroid disease, the specific nature and relative prevalence of these disorders and the utility of nuclear imaging and other studies in their detection remains unclear. PATIENTS AND METHODS The authors performed a retrospective study of 50 patients with endogenous subclinical thyrotoxicosis. The results of the history and physical examination, thyroid nuclear scan, radioactive iodine uptake measurement, and thyroid antibody studies were reviewed. The results of the nuclear imaging and thyroid antibody studies were combined in an attempt to establish an underlying diagnosis for each patient. RESULTS The thyroid nuclear imaging and antibody studies were used to establish a specific thyroid disorder in most of the patients (n = 39). These disorders included most commonly toxic multinodular goiter, various forms of autoimmune thyroid disease, and solitary toxic adenoma. A specific diagnosis was not determined in 11 patients. Therapy with I-131 radioactive iodine was administered to 14 of these patients, 13 of whom subsequently achieved a normal thyroid-stimulating hormone level. CONCLUSIONS Most patients with endogenous subclinical thyrotoxicosis have underlying thyroid abnormalities that can be determined by nuclear imaging and, in selected cases, thyroid antibody studies.

Hypermetabolism on F-18 FDG PET of multiple pulmonary nodules resulting from bronchiolitis obliterans organizing pneumonia

Abstract:There have been multiple reports of benign thoracic conditions demonstrating hypermetabolism on F-18 FDG PET scans, including granulomatous infection, benign tumors, and autoimmune diseases, but bronchiolitis obliterans organizing pneumonia (BOOP) is not a well-known cause of such hypermeta

False-positive I-131 uptake by an ovarian serous cystadenofibroma.

We present the case of a 53-year-old woman after thyroidectomy with metastatic multifocal papillary carcinoma and encapsulated focal Hurthle cell carcinoma. Postoperatively, an I-131 whole-body scan revealed uptake in the low midline anterior neck. She was treated with 151.5 mCi of I-131. The 1-year follow-up I-131 whole-body scan revealed a new pelvic mass with I-131 uptake. Pelvic CT showed bilateral complex ovarian masses. She underwent surgical excision, revealing a right ovarian endometriotic cyst and a left ovarian cystadenofibroma, without thyroid tissue involvement. I-131 uptake in a cystadenofibroma is extremely rare and has been reported only once to our knowledge.

Primary testicular lymphoma involving the spermatic cord and gonadal vein.

We report a case of a 70-year-old man with a history of prostatic adenocarcinoma and a 3-month history of right hemiscrotal swelling. The patient underwent a CT scan, scrotal ultrasound, and F-18 FDG-PET scan to evaluate for metastatic prostate cancer. The CT scan demonstrated an ill-defined soft-tissue mass extending along the right gonadal vein. Scrotal ultrasound revealed a heterogeneous right testicular mass. The F-18 FDG-PET scan demonstrated intense hypermetabolic activity along the course of the right gonadal vein extending to the right hemiscrotum. Subsequent right radical orchiectomy and pathologic examination revealed a B-cell lymphoma, infiltrating the testicular parenchyma, spermatic cord, gonadal vessels, and adjacent soft-tissues. Lymphoma or other tumors rarely infiltrate the spermatic cord, and have only very rarely been demonstrated on PET imaging.

Progression of clinically stable lymphedema on lymphoscintigraphy.

Lymphedema is due to dysfunction in lymphatic transport, and is divided into primary and secondary subtypes. Primary lymphedema is a congenital lymphatic abnormality or dysfunction whereas secondary lymphedema is characterized by pathologic disruption or obstruction of a previously-normal lymphatic system. The stage of lymphedema is determined clinically. Lymphoscintigraphy, however, may be used to assess disease extent, for early detection of disease progression, and can be used to direct therapy. We report a case of a 56-year-old woman with clinically stable lymphedema of 5 years, yet with lymphoscintigraphy findings compatible with disease progression.

Giant splenic hemangioma: confirmation of diagnosis with labeled erythrocyte scintigraphy

PURPOSE: To assess the use of a Tc-99m erythrocyte-labeled SPECT scan to characterize a giant splenic hemangioma. METHODS: A patient clinically mistaken to have a myelodysplastic disorder underwent a contrast-enhanced CT followed by a Tc-99m erythrocyte-labeled SPECT scan. RESULTS: CT showed a heterogeneous vascular lesion arising in the spleen. Percutaneous biopsy was nondiagnostic. A Tc-99m erythrocyte-labeled SPECT study revealed findings consistent with a giant splenic hemangioma, which was subsequently confirmed at surgery. CONCLUSION: A Tc-99m erythrocyte-labeled SPECT scan may be very useful in confirming the diagnosis of a large or giant splenic hemangioma.

Intensely hypermetabolic lipomatous hypertrophy of the interatrial septum on 18-FDG PET with MRI and CT correlation.

We present a 69-year-old female patient with a history of emphysema, rosacea, and breast cancer. The patient was in remission for 4 years until a 15-pound weight loss prompted further evaluation with a computed tomography of the chest, abdomen, and pelvis, cardiac magnetic resonance imaging, as well as an 18-FDG-PET scan to evaluate for metastatic disease and potential cardiac abnormalities. There was an intensely hypermetabolic bilobed focus within the region of the interatrial septum, correlating with the patient’s lipomatous hypertrophy of the interatrial septum (LHIS), which was identified on computed tomography and magnetic resonance imaging. LHIS is a relatively uncommon cardiac finding characterized by excessive deposition of adipocytes with varying quantities of brown fat. Brown fat in LHIS may be hypermetabolic on 18-FDG-PET examinations, and familiarity with the prevalence and features of LHIS will avoid misdiagnosis of metastatic disease.

McCune-Albright Syndrome: intensely hypermetabolic polyostotic fibrous dysplasia on F-18 FDG-PET.

We present a 30-year-old woman with a medical history of McCune-Albright Syndrome who underwent an F-18 FDG-PET scan for further evaluation of cervical adenopathy noted on a recent computed tomographic examination. Intensely hypermetabolic foci were noted in the axial and appendicular osseous structures, correlating with foci of polyostotic fibrous dysplasia seen on CT scan. Increased uptake of Tc-99 MDP or HDP in polyostotic fibrous dysplasia is well described. The potential for misdiagnosis of intensely hypermetabolic foci involving fibrous dysplasia on F-18 FDG-PET scan has also been described. This is a rare case of FDG-PET hypermetabolism of polyostotic fibrous dysplasia in the setting of McCuneAlbright Syndrome.

Supernumerary left kidney

A 77-year-old woman with a history of right breast cancer and recently diagnosed B-cell lymphoma was evaluated for developing renal insufficiency with ultrasound and a Tc-99m MAGS renal scan. These studies demonstrated the presence of 3 functioning native kidneys. Supernumerary kidneys are a very rare congenital anomaly, and the use of renal scintigraphy plays an important role in both the diagnosis and the evaluation of renal function in such patients.