Follicular thyroid cancer is the second-most common type of thyroid cancer after papillary thyroid cancer. Metastases to the mandible and maxillofacial region are rare. Our study presents a 55-year-old patient who underwent total thyroidectomy for follicular thyroid cancer and subsequent radioactive iodine therapy. Sixteen years after diagnosis, elevated thyroglobulin levels suggested disease recurrence. Using advanced imaging techniques - Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography scan, bone scintigraphy, and posttreatment I-131 scan-an unexpected metastatic site was identified: the left mandibular condyle. A biopsy confirmed the presence of metastatic follicular thyroid cancer.

Giardia lamblia is an intestinal protozoan with oral-fecal transmission. Infection is predominantly located in the small intestine. Giardiasis causes intraepithelial lymphocytosis in the small intestine which causes false-positive fluorodeoxyglucose (FDG) uptake mimicking malignancy. We present here an interesting image of fluorine-18 FDG positron emission tomography/computed tomography showing jejunal uptake caused by giardiasis in a known case of lymphoma.

Erdheim-Chester disease (ECD) is a systemic histiocytosis that can involve several organs, with severity ranging from occult to life-threatening. The disease was first described by William Chester in 1930 after working with the Austrian pathologist Jakob Erdheim. Even today, a correct diagnosis of ECD often takes years, given the rarity and variable manifestations of ECD. We present a case of a 63-year-old female presenting with multiple brain lesions, sent for fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography to find primary, and it showed hypermetabolic right occipital brain lesion, right orbital lesion, and soft tissue around the arch of the aorta (coated aorta), and final histopathology of the brain lesion confirmed histiocytosis ECD.

Burkitt lymphoma (BL) is a poorly differentiated, aggressive form of B-cell non-Hodgkin\'s lymphoma. The clinical presentation of this disease is varied and may be nodal, extranodal, or both. BL of the breast, either primary or secondary, with bilateral breast involvement, is extremely rare. Herein, we present a case of BL in a 27-year-old male with unusual bilateral breast involvement.

Tracheal metastases from renal cell carcinoma (RCC) are extremely rare. Most common primary malignancy metastasizing to this unusual location usually comes from lung region while it is rare to have tracheal metastases from nonpulmonary malignancies such as breast, thyroid, colorectal carcinoma, and melanoma. The lesions detected on fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) scan, especially in the head and neck region, soft tissue, and muscular compartment during follow-up of RCC patients raise the possibility of metastatic lesions in these regions, though rarely encountered. F-18 FDG PET/CT proved to be a valuable noninvasive imaging tool in detecting the very unusual distant metastases and multisystem involvement many years after nephrectomy in RCC in a single session in the present case.

Bone scintigraphy with 99mTc diphosphonates may exhibit extraosseous lesions in addition to metastatic lesions. Multiple factors can affect extraosseous 99mTc methylene diphosphonate (MDP) uptake. Similar uptake pattern of 99mTc MDP and fluorine-18 fluorodeoxyglucose (18F FDG) in hepatic metastasis was not already notified. In our case, initial tumor necrosis and subsequent intracellular calcification resulted in similar 99mTc MDP and 18F FDG accumulation in the metastatic area.

The role of fluorine-18 fluorodeoxyglucose. (18F-FDG) positron emission tomography. (PET)/computed tomography. (CT) in the initial staging of various malignancies is now well established. However, nonspecificity of FDG occasionally results in tracer uptake in benign lung lesions. The authors describe a complicated case of carcinoma stomach with multiple nodules and a cavitary lesion in lungs where 18F-FDG PET CT done for initial staging revealed FDG avid mass in stomach, FDG avid multiple mediastinal lymph nodes and multiple intensely FDG avid bilateral lung lesions. The FDG avid lung lesions turned out to be due to silicosis as confirmed by histopathology.

Primary adrenal lymphoma (PAL) is a rare malignancy often involving bilateral adrenal glands. Diffuse large B-cell is the most common histological type. Unilateral presentation and T-cell/natural killer (T/NK) cell histological type is rarer. We report fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography scan findings in a case of unilateral T/NK cell PAL performed for staging and interim treatment response assessment.

Parapharyngeal space (PPS) tumors are rare and account for about 0.5% of all head and neck neoplasms. Most PPS tumors are benign (up to 80%) while the remaining 20% are malignant. These tumors are either primaries; most commonly arising from salivary glands or metastatic tumors or due to direct extension of tumors from the adjacent sites. Distant metastasis from breast cancers more commonly involves the lungs, bones, brain and liver. Metastasis to the PPS from a primary breast carcinoma is rare, with only one case reported in literature. We, to the best of our knowledge report the second case of a carcinoma breast metastasizing to the PPS and further discuss the diagnostic and therapeutic challenges involved in its management. A fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography scan apart from explicitly defining the extent of the PPS tumor, majorly influenced the therapeutic decision making process by ruling out other sites of metastasis.

OBJECTIVE: The present study was undertaken to evaluate the diagnostic utility of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in patients presenting as pyrexia of unknown origin (PUO).
METHODS: Forty-seven patients (31 males and 16 females; mean age of 42.7 ± 19.96 years) presenting as PUO to the Department of Medicine at the All India Institute of Medical Sciences, New Delhi over a period of 2 years underwent F-18 FDG PET/CT. PET ⁄ CT was considered supportive when its results correlated with the final definitive diagnosis. Final diagnosis was made on the basis of combined evaluation of history, clinical findings, investigations, and response to treatment.
RESULTS: Thirty-five PET/CT studies (74.5%) were positive. However, only 18 (38.3%) were supportive of the final diagnosis. In three patients (6.4%), PET/CT was considered diagnostic as none of the other investigations including contrast-enhanced computed tomography of chest and abdomen, and directed tissue sampling could lead to the final diagnosis. All these three patients were diagnosed as aortoarteritis.
CONCLUSIONS: Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography is an important emerging modality in the workup of PUO. It supported the final diagnosis in 38% of our patients and was diagnostic in 6.4% of patients. Thus, PET/CT should only be considered as second-line investigation for the diagnostic evaluation of PUO; especially in suspected noninfectious inflammatory disorders.