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We describe the case of an unvaccinated 21-year-old Japanese male who experienced psychotic symptoms attributed to encephalopathy, known as post-acute COVID-19 syndrome (PACS). One week after his discharge following the remission of a SARS-CoV-2 infection, he experienced hyperactive delirium and unexpected movements of his limbs. As COVID-19-associated encephalopathy was suspected as a cause of the psychotic symptoms, he was admitted to the Department of Neurology. He received antiviral and steroid pulse therapy, but his psychiatric symptoms did not improve completely. Consequently, he was admitted to our psychiatric ward with a diagnosis of a primary psychotic disorder. Although he did not take psychopharmacotherapy, he gradually achieved a remission of psychiatric symptoms. At three months post-SARS-CoV-2 infection, single-photon emission computed tomography (SPECT) revealed hypoperfusion in the bilateral cerebellar dentate nuclei and occipital lobes. However, no abnormal findings were observed on fluorine-18 fluoro-deoxy-glucose positron emission tomography ( 18 F-FDG PET) at six months after the infection. This case indicates that (1) brain perfusion SPECT can be effective for detecting functional alterations in post-acute COVID-19-associated encephalopathy, and (2) it is necessary to carefully monitor patients' progress instead of quickly diagnosing a primary psychotic disorder., Competing Interests: The authors have declared financial relationships, which are detailed in the next section., (Copyright © 2024, Ikemizu et al.)

Soft tissue mucosa-associated lymphoid tissue (MALT) lymphoma is a rare type of marginal zone lymphoma. Herein, we report a case of a 61-year-old patient who developed soft-tissue marginal zone lymphoma in the right arm. He was treated with rituximab-chlorambucil with good metabolic response and no evidence of disease recurrence after one year of follow-up., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Hammani et al.)

Nasal squamous cell carcinoma (SCC) is rare and aggressive. It often requires combination treatment. Precise post-treatment disease assessment is vital for determining the subsequent management and prognosis. We present the intriguing case of a 52-year-old man with T4bN0M0 stage IVB SCC. Post-treatment fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) findings indicated a complete response; however, microscopic remnants of the cancer were detected during endoscopic sinus surgery. This report underscores the limitations of post-treatment assessment using FDG PET-CT and outpatient endoscopy alone due to these modalities' potential inability to detect microscopic residual disease. Endoscopic sinus surgery should be incorporated into routine post-treatment assessments of nasal SCC to improve disease detection and guide further treatment. Further large-scale studies are required to confirm these findings., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Tsuda et al.)

Hodgkin's lymphoma (HL), also known as Hodgkin lymphoma or Hodgkin disease, is a type of malignancy that originates in B lymphocytes, which are a type of white blood cells involved in the immune system. It is characterized by the presence of abnormal Reed-Sternberg cells within the lymph nodes or other lymphoid tissues. Bone involvement of HL is exceptional, which can be localized or part of a disseminated disease. The case of our patient is a Hodgkin's lymphoma initially presenting with a complaint of myalgia. Magnetic resonance imaging and 8F-fluorodeoxyglucose positron emission tomography (FDG PET) played a crucial role in the diagnosis of this rare case., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Chergaoui et al.)

Inflammatory myofibroblastic tumors (IMT) are a rare set of tumors that have been reported in various areas of the body but not quite as often in systemic lymph nodes. Herein, we discuss the case of a 60-year-old woman who presented with bilateral cervical and axillary lymphadenopathy and a low-grade fever. She subsequently underwent a fluorine-18-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET-CT) as part of her evaluation. The scan revealed multiple hypermetabolic cervical, axillary, mediastinal, retroperitoneal, pelvic, and inguinal lymph nodes of various dimensions scattered throughout her body. Based on these findings, she was erroneously diagnosed to have lymphoma. It was only after histopathological correlation was the diagnosis revised to that of IMT, after which she was started on a course of oral corticosteroids. On follow-up imaging, she showed evidence of complete resolution of the involved lymph nodes. She has been disease-free for the past nine months after completing treatment. This case highlights the importance of including IMT as part of the differential diagnosis in suspected cases of lymphoma, giving credence to the phrase "all that glitters is not gold.", Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Wakankar et al.)

Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)/coronavirus disease 2019 (COVID-19) infection predominantly affects the respiratory system, it has also been found to be responsible for several gastrointestinal effects due to its capability to attack angiotensin-converting enzyme (ACE) type 2 cells in various parts of the body. Several cases of radiologically confirmed thyroiditis, axillary lymphangitis, and acute pancreatitis related to COVID-19 infection have been reported, which seem to arise from a direct cytotoxic effect of the virus itself. This case report presents an incidental 18-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) computed tomography (CT) finding of mild pancreatic inflammation/pancreatitis in an otherwise asymptomatic patient undergoing routine imaging as part of the staging process following stem cell transplant, who had recently recovered from a severe form of COVID infection. This case highlights the fact that COVID can trigger insidious inflammatory processes in a variety of organs often remaining clinically undetectable until resultant end-organ damage causes incipient clinical symptoms., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Qurban et al.)

Imaging is useful in identifying the primary site of an unknown primary cancer, and 18 F-fluorodeoxyglucose positron emission tomography/computed tomography ( 18 F-FDG PET/CT) is an excellent imaging modality for identifying the primary lesion. However, a potential limitation is that 18 F-FDG is physiologically excreted from the kidneys, thus masking renal lesions. In this report, we describe two cases of cancer of unknown origin that were detected as originating from renal cancer on 18 F-FDG PET/CT. Both cases showed abnormal nodular accumulation of 18 F-FDG in the kidney, which can be distinguished from the physiological excretion of 18 F-FDG in the urinary tract. It is clinically crucial to be able to confirm the possibility of renal cancer, and careful observation of the urinary tract with 18 F-FDG PET/CT can be useful., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Kono et al.)