IgG4 Antibodies Induced by Repeated Vaccination May Generate Immune Tolerance to the SARS-CoV-2 Spike Protein.

Less than a year after the global emergence of the coronavirus SARS-CoV-2, a novel vaccine platform based on mRNA technology was introduced to the market. Globally, around 13.38 billion COVID-19 vaccine doses of diverse platforms have been administered.

Disseminated Multi-system Sarcoidosis Mimicking Metastases on F-FDG PET/CT.

A 60-year-old female with no significant medical history presented with hematuria. A computed tomography (CT) scan revealed extensive lymphadenopathy with hypodensities in the liver and spleen, and she was referred for an F-fluorodeoxyglucose (F-FDG) positron emission tomography/CT (PET/CT) study to assess for malignancy of unknown primary. PET/CT revealed extensive F-FDG avid lymphadenopathy as well as innumerable intensely F-FDG avid lung, liver and splenic nodules, highly concerning for malignancy.

Primary Thyroid Lymphoma: External Beam Radiation Therapy Induced Thyroiditis Mimics Residual Disease on Serial F-FDG PET/CT Imaging.

A 67-year-old female patient with no prior history of benign thyroid disease was diagnosed with primary thyroid lymphoma and was staged with F-fluoro-2-deoxy-D-glucose (F-FDG) positron emission tomography/computed tomography (PET/CT). She was treated with chemotherapy and external beam radiation therapy, and a follow-up PET/CT showed significant reduction in the size of the thyroid lymphoma with persistent intense F-FDG uptake, which was interpreted as partial response to therapy. However, two subsequent PET/CT studies showed no change in the persistent intense F-FDG uptake in the thyroid and a biopsy confirmed the presence of thyroiditis with no evidence of residual lymphoma.

Inflammatory and Ischemic Post Liver Transplant Complications Mimic Malignancy on F-FDG PET/CT.

A 65-year-old male patient with a one year history of liver transplantation was referred for an F-fluoro-2-deoxy-D-glucose (F-FDG) positron emission tomography/computed tomography (PET/CT) to rule out post transplant lymphoproliferative disease. Multiple foci of intense abnormal F-FDG uptake were seen in the transplanted liver which were concerning for malignancy. Explantation of the liver approximately 1 month following the PET/CT revealed multiple inflammatory and ischemic changes including large bile duct necrosis, acute cholangitis, bile duct obstruction changes and periportal fibrosis, with no evidence of malignancy.

Unilateral Muscle Artifacts due to Non-compliance During Uptake Phase of F-FDG PET/CT in an Oncologic Patient.

A 49-year-old male patient with a prior history of poor compliance with medical appointments was referred for an F-fluoro-2-deoxy-D-glucose (F-FDG) positron emission tomography/computed tomography (PET/CT) for the staging of a rectal squamous cell carcinoma. The PET/CT showed unilateral diffuse skeletal muscle F-FDG uptake as well as bilateral salivary gland uptake artifacts, suggestive of non-compliance with patient preparation instructions. The PET/CT nurse noted that during the F-FDG uptake phase, the patient appeared intoxicated, and she found two beer cans hidden in the waste disposal beside his chair just prior to imaging.

Systemic Lupus Erythematosus Associated Pitfalls on F-FDG PET/CT: Reactive Follicular Hyperplasia, Kikuchi-Fujimoto Disease, Inflammation and Lymphoid Hyperplasia of the Spleen Mimicking Lymphoma.

Systemic lupus erythematosus (SLE) is associated with a variety of inflammatory processes that can affect the lymph nodes, brain, kidneys, and spleen. We present two patients with SLE in whom SLE-associated conditions complicated interpretation of F-fluoro-2-deoxy-d-glucose (F-FDG) positron emission tomography/computed tomography (PET/CT) imaging of the lymph nodes and the spleen. The imaging findings mimicked lymphoma, but histopathological evaluation showed benign processes including reactive follicular hyperplasia in the lymph nodes, Kikuchi-Fujimoto disease in perisplenic lymph nodes, and inflammatory changes and lymphoid hyperplasia in the spleen.

Primary Renal Leiomyosarcoma Presenting with Subcutaneous and Osseous Metastases: Staging and Follow-Up with 18F-FDG PET/CT.

A 60 year old woman who presented with multiple small subcutaneous nodules in the upper back and arms, was referred for an [18F] fluoro-2-deoxy-D-glucose (F-FDG) positron emission tomography/computed tomography (PET/CT) after histological evaluation revealed metastatic leiomyosarcoma of unknown origin. The PET/CT showed multiple F-FDG-avid subcutaneous nodules, bone lesions, as well as a large left renal mass, which was biopsied to confirm a primary renal leiomyosarcoma arising from the renal parenchyma. A post therapy PET/CT showed overall progression of disease.

Recurrent Follicular Dendritic Cell Sarcoma of the Parotid Gland Imaged with 18F-FDG PET/CT.

Follicular dendritic cell sarcoma (FDCS) is an extremely rare tumor with only 67 cases of head and neck FDCS reported in the literature. A 65-year-old female had a 6-cm follicular dendritic cell sarcoma resected from the left parotid gland with close margins. It recurred 1 year later as a 5-cm mass that was intensely [18F] fluoro-2-deoxy-D-glucose (18F-FDG) avid on positron emission tomography/computed tomography (PET/CT) and was re-excised.

Thyroid Incidentalomas on F-FDG PET/CT: Clinical Significance and Controversies.

Objective: The purpose of the current study is to examine the incidence and clinical significance of unexpected focal uptake of F-fluorodeoxyglucose (F-FDG) on positron emission tomography/computed tomography (PET/CT) in the thyroid gland of oncology patients, the maximum standardized uptake value (SUV) of benign and malignant thyroid incidentalomas in these patients, and review the literature.

Methods: Seven thousand two hundred fifty-two F-FDG PET/CT studies performed over four years, were retrospectively reviewed. Studies with incidental focal F-FDG uptake in the thyroid gland were further analyzed.

Composite Cutaneous Lymphoma (Iatrogenic Immunodeficiency-Associated Lymphoproliferative Disorder) in a Patient with Rheumatoid Arthritis Treated with Methotrexate: Staging and Evaluation of Response to Therapy with F-FDG PET/CT.

A 67 year old woman with a 10 year history of rheumatoid arthritis (RA) treated with methotrexate and prednisone, presented with a 2 year history of worsening multiple cutaneous plaques of variable appearance. Two distinct skin lesions were biopsied to reveal a composite cutaneous lymphoma, possibly caused by long term methotrexate therapy. An [18F] fluoro-2-deoxy-D-glucose (F-FDG) positron emission tomography/computed tomography (PET/CT) was performed to stage the malignancy, and was later repeated to evaluate response to chemotherapy, which guided subsequent management.

Clinical Significance of F-Fluorodeoxyglucose Avid Prostate Gland Incidentalomas on Positron Emission Tomography/Computed Tomography.

Objective: The aim of this study was to evaluate the clinical significance of incidental focal uptake of F-fluorodeoxyglucose (F-FDG) on positron emission tomography/computed tomography (PET/CT) in the prostate glands of cancer patients.

Methods: A retrospective review of 3122 consecutive male patients who underwent F-FDG PET/CT studies with an oncologic indication, over the course of four years, was performed. Studies with incidental F-FDG uptake in the prostate gland were further analyzed.

Pleomorphic spindle cell sarcoma (PSCS) (formerly known as malignant fibrous histiocytoma, MFH) of the spleen, mimics an atypical haemangioma on Tc-RBC, CT and Ultrasound: staging with F-FDG PET/CT.

A 63-year-old male was found to have a 7.5-cm splenic mass that had imaging appearances of an atypical haemangioma on CT, ultrasound and a Tc-RBC scan, and he was followed conservatively with serial ultrasounds. Sixteen months later, however, the splenic lesion grew and he developed numerous new liver masses which were biopsy confirmed to be a pleomorphic spindle cell sarcoma (PSCS), formerly known as malignant fibrous histiocytoma (MFH).

Follicular lymphoma transforming into diffuse large B-cell lymphoma in spleen: Simultaneous appearance of both on F-FDG PET/CT and histology.

Low grade lymphoma may transform into a more aggressive lymphoma and this transformation is usually associated with a poor outcome. A 65year old man presented with two metabolically active splenic lesions on a staging [18F] fluoro-2-deoxy-d-glucose (F-FDG) positron emission tomography/computed tomography (PET/CT). Histologic evaluation post splenectomy confirmed the presence of two clonally related lymphomas: a follicular lymphoma (FL) and a diffuse large B-cell lymphoma (DLBCL).

131I-MIBG Therapy in a Metastatic Small Bowel Neuroendocrine Tumor Patient Undergoing Hemodialysis.

Systemic radioisotope therapy with I-metaiodobenzylguanidine (I-MIBG) is an effective form of targeted therapy for neuroendocrine tumors. One of the absolute contraindications to administering I-MIBG therapy listed in the 2008 European Association of Nuclear Medicine guidelines is renal insufficiency requiring dialysis, although this contraindication is not evidence based. We describe a 68-year-old woman with a metastatic small bowel neuroendocrine tumor who developed renal insufficiency requiring hemodialysis.

Cerebral and pulmonary lymphomatoid granulomatosis and EBV positive oesophageal ulcer in an immunosuppressed renal transplant patient staged and followed with serial MRI and F-FDG PET/CT after rituximab therapy.

Lymphomatoid granulomatosis is a rare Epstein-Barr virus-related lymphoproliferative disorder. We describe a case of a 42-year-old female with lupus nephritis and immunosuppression post renal transplant, who was diagnosed with central nervous system and lung lymphomatoid granulomatosis, as well as an Epstein-Barr virus-positive oesophageal ulcer, and was staged and followed up long term with multiple F-fludeoxyglucose positron emission tomography/CT scans and brain MRIs after achieving a complete metabolic response with rituximab.

Appearance of CNS histoplasmosis on F-FDG PET/CT with MRI correlation.

Disseminated histoplasmosis is an opportunistic infection encountered in immunocompromised patients such as those with human immunodeficiency virus infection/acquired immune deficiency syndrome. Involvement of the central nervous system (CNS) can occur in 5-20% of cases of disseminated histoplasmosis, and CNS histoplasmosis can be very difficult to diagnose conventional imaging modalities such as CT or MRI. The role of F-fludeoxyglucose positron emission tomography/CT scan in the diagnosis of CNS histoplasmosis has not been established.

Extensive polyostotic fibrous dysplasia evaluated for malignant transformation with Tc-MDP bone scan and F-FDG PET/CT.

Fibrous dysplasia accounts for approximately 7% of benign bone tumours and is a developmental disorder of unknown aetiology. Malignant transformation has been reported in 0.4% of all cases of fibrous dysplasia, and the use of F-fludeoxyglucose positron emission tomography/CT scan in the evaluation of malignant transformation has not yet been established.

Intra-abdominal desmoplastic small round cell tumour: staging and surveillance with F-FDG PET/CT following peritonectomy and HIPEC.

Intra-abdominal desmoplastic small round cell tumours are rare aggressive tumours of mesothelial origin with less than 60 cases reported in the literature. They are difficult to treat and the role of F-fludeoxyglucose positron emission tomography (PET)/CT scan in their management has not been established. A 41-year-old male presented with a 21-cm desmoplastic small round cell tumour and was managed with radiotherapy, surgery and chemotherapy, with each treatment monitored and guided by F-fludeoxyglucose PET/CT scan.

MUGA image artefacts caused by metallic injection ports in breast reconstruction tissue expanders: a report of two breast cancer patients.

Expander-based breast reconstruction is a popular form of post-mastectomy reconstruction and involves the temporary subcutaneous implantation of breast tissue expanders that require periodic, incremental inflation with sterile saline by injection until the desired amount of tissue is developed. One type of tissue expander injection port system currently on the market is made of titanium and rare-earth magnets that enhance injection accuracy. These highly dense metallic materials, however, can cause attenuation artefacts on multiple gated acquisition cardiac studies.

Klippel-Feil Syndrome With Spinal Dysraphism: Diastematomyelia on 18F-NaF Bone PET, CT, and MRI Imaging.

A 49-year-old woman with known Klippel-Feil syndrome had a CT scan for staging of stage IIIA invasive carcinoma of the left breast. She was found to have cervicothoracic spinal dysraphism with diastematomyelia. An F-NaF bone PET done as part of the metastatic workup showed the characteristic sagittal bone spur, and MRI demonstrated a complete split of the cervical and upper thoracic spinal cord, previously unknown to the patient.

Metastatic Insulinoma Pancreatic Neuroendocrine Tumor Treated With 177Lu-DOTATATE Induction and Maintenance Peptide Receptor Radionuclide Therapy: A Suggested Protocol.

A 70-year-old woman presented with frequent episodes of hypoglycemia. Imaging revealed a 6-cm pancreatic mass with several liver lesions. The pancreatic mass was resected and confirmed to be a well-differentiated insulinoma.