Pediatric adrenocortical carcinoma (ACC) is rare malignancy, and its oncocytic variant is exceptionally rare in infants. A 1-year-old girl presented with excessive hair growth and hoarseness of voice for 8 months of age. Investigations revealed elevated androgen levels, and whole-body 18F FDG PET-CT imaging showed an isolated large left adrenal mass. The mass was surgically excised, and histopathology confirmed oncocytic adrenocortical carcinoma with a Wieneke score of 5, indicating malignancy. The postoperative course was uneventful with stabilization on antihypertensive and corticosteroid therapy.

Gilal fibrillary acidic protein (GFAP) meningomyelitis is a rare autoimmune inflammatory disorder of the central nervous system, typically presenting with subacute encephalopathy, ataxia, optic neuritis, and cerebrospinal fluid (CSF) pleocytosis. It is characterized by the presence of GFAP-specific autoantibodies, which target astrocytes and cause widespread neuroinflammation. 18F-FDG PET/CT plays a critical role in the early diagnosis of autoimmune encephalitides, particularly in cases where conventional MRI findings may be subtle or nonspecific. Here, we present a case of 21-year-old woman who presented with early morning occipital headache with fever, followed by progressive drowsiness and acute urinary retention. On clinical examination, meningeal signs were positive. MRI brain was suggestive of leptomeningeal enhancement involving the brain and spinal cord, and 18F-FDG PET/CT was done for further evaluation.

A 75-year-old man with a history of renal cell carcinoma presented with dyspnea and an elevated D-dimer (4500 ng/mL). Clinical assessment suggested pulmonary embolism. Due to renal impairment (creatinine 2.1 mg/dL), CT angiography was contraindicated. Noncontrast chest CT revealed hyperdense intraluminal material in bilateral main pulmonary arteries, consistent with acute thromboemboli. Fresh clots appear hyperdense due to high hemoglobin concentration and reduced plasma content. Subsequent lung perfusion SPECT demonstrated multiple large bilateral perfusion defects, confirming high-burden pulmonary embolism. This case illustrates the diagnostic utility of the hyperdense pulmonary artery sign complemented by perfusion scintigraphy in patients where contrast angiography is contraindicated.

We report a case involving a 66-year-old man with prostate adenocarcinoma, referred for initial staging using 99mTc-PSMA and 99mTc-MDP bone scan. The whole body PSMA scan revealed foci of increased tracer uptake in the right knee and the surrounding periarticular space above the knee. Subsequent 99mTc-PSMA SPECT/CT imaging demonstrated evidence of arthritis characterized by effusion in the periarticular region, connected to the joint in the right knee. Notably, the patient had received an intra-articular corticosteroid injection just 2 days before the scan. This case highlights the necessity of recognizing atypical 99mTc-PSMA uptake patterns to differentiate from metastasis, thereby enhancing diagnostic accuracy.

In medullary thyroid carcinoma (MTC), skeletal metastases are present in 19% of patients at initial diagnosis and increase up to 29% during follow-up, predominantly involving the spine and pelvis. We describe 2 patients of metastatic MTC illustrating divergent lesion morphologies: one exhibiting sclerotic bone metastases and the other displaying marrow and lytic lesions. The lytic and marrow-based metastases demonstrated more avidity for [ 18 F]F-FDG PET/CT, whereas [ 68 Ga]Ga-DOTA-FAPI-04 PET/CT provided enhanced visualization of the sclerotic lesions. This dichotomous tracer behaviour underscores the importance of tailoring PET agent selection to lesion morphology, potentially optimizing diagnostic accuracy and guiding individualized management strategies.

We present a case of a 36-year-old man with medullary thyroid carcinoma (MTC) who developed lung metastases 10 years post-total thyroidectomy. He presented with cough, and to evaluate his eligibility for peptide receptor radionuclide therapy (PRRT), a 99mTc-HYNIC-octreotide scan was conducted. The scan revealed multiple metastatic lymph nodes, lung metastases, and a solitary hepatic metastasis, all with mild octreotide avidity. Following 2 cycles of PRRT, minimal response was observed, and the lesions lost avidity. A subsequent 99mTc-FAPI scan demonstrated favorable uptake in the metastatic lesions, including a non-octreotide-avid hepatic lesion, suggesting the potential utility of FAPI-based radiopharmaceuticals for MTC management.

A 2-year-old girl with Beckwith-Wiedemann syndrome (BWS) underwent 18 F-FDG PET/CT for differential diagnosis of a left adrenal lesion. The imaging revealed moderate 18 F-FDG uptake in the left adrenal gland, accompanied by regional lymphadenopathy. Histopathologic examination confirmed the diagnosis of neuroblastoma. One year following multimodal therapy, follow-up 123 I-MIBG SPECT/CT did not demonstrate any abnormal MIBG accumulation. This case highlights the diagnostic and staging utility of 18 F-FDG PET/CT in pediatric BWS patients with neuroblastoma.

Mantle cell lymphoma (MCL) is a rare and aggressive subtype of non-Hodgkin lymphoma that typically presents with lymphadenopathy and extranodal involvement, most commonly affecting the spleen and gastrointestinal tract. Skeletal muscle infiltration is exceedingly rare, particularly in MCL. We report the case of a 64-year-old woman with MCL who initially achieved complete metabolic remission following R-CHOP chemotherapy and rituximab maintenance. However, restaging with 18F-FDG PET/CT revealed extensive skeletal muscle recurrence. This case underscores the critical role of 18F-FDG PET/CT in identifying atypical relapse patterns in MCL and highlights the need for vigilant, long-term surveillance following therapy.

This study demonstrates the clinical utility of multitracer positron emission tomography (PET) imaging with 18F-FDG, 68Ga-FAPI-04, and 68Ga-PSMA-11 PET/CT in a rare case of metastatic renal cell carcinoma (RCC) involving the sigmoid colon. A 70-year-old man, who had undergone nephrectomy for T2aN0, RCC in 2019, presented with progressive weight loss and altered bowel habits. Contrast-enhanced computed tomography of the abdomen and pelvis (CECT A+P) revealed a suspicious ulcero-proliferative lesion in the distal sigmoid colon. Functional imaging with 18F-FDG, 68Ga-FAPI-04, and 68Ga-PSMA-11 PET/CT demonstrated focal tracer uptake in the colonic lesion, providing additional evidence suggestive of a neoplastic process. Colonoscopic biopsy subsequently confirmed the lesion to be metastatic RCC. This case highlights the complementary role of multitracer PET imaging in characterizing atypical and rare site metastatic presentations, with its potential theranostic implications.

A 5-year-old boy presented with epileptic seizures persisting for ~3 months. To localize the epileptogenic focus, 18F-FDG PET/CT imaging was performed. Brain PET/CT revealed increased 18F-FDG uptake in the right frontal lobe, which was consistent with the clinical manifestations observed during the seizure phase. The torso PET/CT identified a mass in the right adrenal region exhibiting moderate 18F-FDG uptake. Histopathologic examination of the right adrenalectomy specimen confirmed the diagnosis of neuroblastoma. The patient remained seizure-free 2 weeks after surgery. In this case, epileptic seizures represent an unusual and rare initial presentation of neuroblastoma, which was incidentally detected by 18F-FDG PET/CT.

A 50-year-old man with a history of a gunshot wound to the skull base in 1997 presented with new secretion from a retroauricular skin defect and clinical signs of a cerebrospinal fluid (CSF) leak. MRI was contraindicated due to retained metallic foreign bodies. [64Cu]Cu-DOTA PET/CT cisternography revealed progressive extravasation of CSF tracer from the posterior fossa toward a mastoid defect, consistent with a CSF leak, but no fistula to the skin. Intraoperative findings confirmed the leak and identified a cholesteatoma within the bullet tract. This case illustrates the complexity of temporal bone gunshot injuries and highlights the diagnostic utility of PET/CT cisternography in detecting CSF leaks.

Based on anatomic imaging, 18F-FDG PET/CT may provide complementary information for distinguishing tumor thrombus from bland thrombus. Although a few cases of 18F-FDG uptake along the superior vena cava (SVC) in SVC syndrome have been reported, PET/CT findings of 18F-FDG uptake extending from the SVC into the right brachiocephalic vein, right subclavian vein, and up to the right internal jugular vein, accompanied by right atrial thrombus, to our knowledge, appear rarely documented. Herein, we report a 67-year-old woman with extensive malignant thrombus extending from the right internal jugular vein into the superior vena cava and right atrial thrombus due to poorly differentiated thyroid carcinoma (PDTC) on 18F-FDG PET/CT.

A 78-year-old man with neuroendocrine neoplasm (NEN) G2 originating from a presacral tailgut cyst was previously treated with surgery, lanreotide and [177Lu]Lu-DOTATATE peptide receptor radionuclide therapy (PRRT). Due to recurrence, confirmed by [68Ga]Ga-DOTA-LM3 PET/CT, which showed local, hepatic, lymph nodal, soft tissue, and cardiac disease, he received 1 cycle of PRRT with somatostatin receptor (SSTR)-antagonist DOTA-LM3 labeled with alpha-emitting Actinium-225. Due to rising levels of bilirubin 2 months after therapy, an endoscopic retrograde cholangiopancreatography diagnosed bile duct stenosis and gastric adenocarcinoma (cause of death). Autopsy findings did not reveal any residual NEN, indicating complete remission after one cycle of alpha-PRRT.

Benign prostatic hyperplasia can show low-grade PSMA uptake, but rarely shows high-grade PSMA uptake. We describe 18F-PSMA-1007 PET/CT and PET/MRI findings in a case of large benign prostatic hyperplasia with chronic inflammatory infiltrates and a high level of serum total prostate-specific antigen (32.6 ng/mL). The large benign prostatic hyperplasia of the transition zone showed heterogeneous signal intensity on the T2-weighted image and heterogeneous intense PSMA uptake with SUVmax of 19. This case indicates that benign prostatic hyperplasia with chronic inflammation can show high-grade PSMA uptake mimicking or masking prostate cancer of the central gland.

An 85-year-old man with right periorbital edema, bloody epiphora, and rhinorrhea underwent nasal endoscopy, revealing a polypoid lesion in the right maxillary sinus. The tissue biopsy revealed dense lymphoplasmacytic infiltration with elevated IgG4-positive plasma cells, consistent with IgG4-related disease. 99mTc-FAPI-46 SPECT/CT was performed and demonstrated intense uptake in the maxillary sinus polyp and along its bony walls, as well as medial orbital and fronto-ethmoidal regions, correlating with CT findings. Fibroblast activation protein inhibitors (FAPI) imaging delineated active fibro-inflammatory disease beyond structural changes, highlighting its potential in detecting osseous involvement in IgG4-related disease.

A 70-year-old man with dysphagia since 2 months, underwent endoscopy, showing distal esophageal edema and furrows. Biopsy was negative for malignancy. F-18 FDG PET/CT showed low-grade distal esophageal uptake with mild smooth wall-thickening on CT scan. Ga-68 FAPI PET/CT was further performed to substantiate diagnosis and delineate repeat biopsy site, which exhibited intense, diffuse esophageal uptake, mimicking malignancy. However, repeat biopsy confirmed eosinophilic esophagitis, conjugated with peripheral eosinophilia (13.6%) and elevated absolute eosinophil count (801 cells/μL). This case, therefore, highlights a false-positive Ga-68 FAPI PET/CT finding in inflammatory esophageal diseases and underscores the need for multimodal correlation to prevent misdiagnosis.

Primary renal NUT carcinoma is exceptionally rare. Herein, we report 68Ga-FAPI-04 PET/CT findings in a 10-year-old girl with this malignancy. The 68Ga-FAPI-04 PET/CT imaging revealed a right renal mass with intense FAPI uptake, accompanied by FAPI-avid retroperitoneal lymphadenopathy and pulmonary metastases. This case highlights the potential of 68Ga-FAPI-04 PET/CT for precise staging of renal NUT carcinoma.

Neuroendocrine carcinoma (NEC) is a rare and aggressive malignancy that most commonly arises from neuroendocrine cells in the gastrointestinal tract and lungs. Primary intracranial NEC is exceedingly rare, with limited cases reported in the literature. We present the FDG PET/CT imaging finding of a rare case of a large primary intracranial NEC involving the cerebral parenchyma, which appeared as a cystic-solid mass with intense FDG uptake in the irregular rim and solid component.

Hypereosinophilia (HE) is a rare disease with complex and diverse causes. Therapeutic strategies for HE differ because of its diverse causes, demanding advanced diagnostic tools for accurate assessment. This study evaluated the role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in determining the etiology of HE.

We present a high-grade well-differentiated NET with large lesions that demonstrated both SSTR and [18F]F-FDG avidity on baseline PET/CT, an outstanding response following 177Lu-DOTATATE-PRRT with complete resolution of SSTR and [18F]F-FDG uptake, and significant size reduction of liver lesions. Non-SSTR and non-[18F]F-FDG-avid change was noted in segment V, demonstrated uptake on [68Ga]Ga-FAPI-04 PET/CT, and confirmed as fibrotic changes post-PRRT. Following PRRT, analysis of [68Ga]Ga-FAPI-04 PET/CT in well-differentiated NET is important to avoid misinterpretation. Benign fibrosis following treatment may show FAPI uptake as a possible source of false-positive findings on [68Ga]Ga-FAPI-04 PET/CT in the evaluation of NET.

While 18F-FDG PET remains effective in detecting inflammatory cell infiltration, FAPI (fibroblast-activated protein inhibitor) PET may offer higher sensitivity in fibroblast-mediated inflammatory conditions such as pancreatitis. We present the case of a 73-year-old woman with metastatic solitary fibrous tumor undergoing molecular imaging for theranostic evaluation. Both 18F-FDG and 68Ga-FAPI46 PET revealed focal uptake in the pancreatic head with peripancreatic fat stranding on low-dose CT. Notably, FAPI PET/CT also demonstrated diffuse pancreatic uptake suggestive of fibroblast-driven inflammation. Subsequent biochemical and clinical findings confirmed acute pancreatitis. This case highlights the potential of FAPI PET/CT in distinguishing pancreatic inflammation from malignancy.