There was a statistically significant correlation between the mitotic count and the SUV(max) as well as between the presence of tumor necrosis and the SUV(max). Although a correlation between the presence of a myxoid component and SUV(max) was shown, it was not found to be statistically significant. These findings improve on the current information in the literature regarding the use of PET/CT for guidance in sarcoma biopsy. Correlating the SUV(max) with histologic markers that also feature prominently in major sarcoma grading systems may help improve the accuracy of grading and of prognostication by allowing the SUV(max) to potentially serve as a surrogate marker in these grading systems, particularly in cases in which there is interobserver disagreement in the pathologic diagnosis or in cases in which the sarcoma cannot be properly classified on the basis of histopathologic evaluation alone.

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. To date, 72.3% of the total population has been injected at least once with a COVID-19 vaccine. As the immunity provided by these vaccines rapidly wanes, their ability to prevent hospitalization and severe disease in individuals with comorbidities has recently been questioned, and increasing evidence has shown that, as with many other vaccines, they do not produce sterilizing immunity, allowing people to suffer frequent re-infections. Additionally, recent investigations have found abnormally high levels of IgG4 in people who were administered two or more injections of the mRNA vaccines. HIV, Malaria, and Pertussis vaccines have also been reported to induce higher-than-normal IgG4 synthesis. Overall, there are three critical factors determining the class switch to IgG4 antibodies: excessive antigen concentration, repeated vaccination, and the type of vaccine used. It has been suggested that an increase in IgG4 levels could have a protecting role by preventing immune over-activation, similar to that occurring during successful allergen-specific immunotherapy by inhibiting IgE-induced effects. However, emerging evidence suggests that the reported increase in IgG4 levels detected after repeated vaccination with the mRNA vaccines may not be a protective mechanism; rather, it constitutes an immune tolerance mechanism to the spike protein that could promote unopposed SARS-CoV2 infection and replication by suppressing natural antiviral responses. Increased IgG4 synthesis due to repeated mRNA vaccination with high antigen concentrations may also cause autoimmune diseases, and promote cancer growth and autoimmune myocarditis in susceptible individuals.

The presence of necrosis and the volume of necrosis, as identified on the staging FDG PET/CT and after adjusting for SUVmax, are strong independent adverse prognostic factors for disease recurrence and death in patients with limb and girdle sarcomas.

A 20-year-old woman, who presented with a several-week history of abdominal pain, was referred for magnetic resonance imaging (MRI) and 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) after an ultrasound showed complex cystic masses arising from both ovaries. The MRI and 18 F-FDG PET/CT imaging characteristics of the ovarian masses were strongly suspicious for malignancy, and the masses were surgically removed. Histopathological evaluation revealed a bilateral tubo-ovarian abscess, with no evidence of malignancy. This case highlights a potentially serious pitfall in the evaluation of suspicious pelvic masses by 18 F-FDG PET/CT, whereby a complex bilateral tubo-ovarian abscess may mimic the PET/CT imaging characteristics of an ovarian or pelvic malignancy.

Purpose A high percentage of paragangliomas express somatostatin receptors that can be utilized for targeted radioisotope therapy. The aim of this study was to describe and discuss the challenges of treating these tumors with 177 Lu-[DOTA 0 ,Tyr 3 ]octreotate (DOTATATE) radioisotope therapy using established protocols. Methods and Results Three paraganglioma patients were treated with 4-5 cycles of 177

Objective:The purpose of the current study is to examine the incidence and clinical significance of unexpected focal uptake of 18F-fluorodeoxyglucose (18F-FDG) on positron emission tomography/computed tomography (PET/CT) in the thyroid gland of oncology patients, the maximum standardized uptake value (SUVmax) of benign and malignant thyroid incidentalomas in these patients, and review the literature.Methods:Seven thousand two hundred fifty-two 18F-FDG PET/CT studies performed over four years, were retrospectively reviewed. Studies with incidental focal 18F-FDG uptake in the thyroid gland were further analyzed.Results:Incidental focal thyroid 18F-FDG uptake was identified in 157 of 7252 patients (2.2%). Sufficient follow-up data (≥12 months) were available in 128 patients, of whom 57 (45%) had a biopsy performed and 71 had clinical follow-up. Malignancy was diagnosed in 14 of 128 patients (10.9%). There was a statistically significant difference between the median SUVmax of benign thyroid incidentalomas (SUVmax 4.8) vs malignant (SUVmax 6.3), but the wide range of overlap between the two groups yielded no clinically useful SUVmax threshold value to determine malignancy.Conclusion:18F-FDG positive focal thyroid incidentalomas occurred in 2.2% of oncologic PET/CT scans, and were malignant in 10.9% of 128 patients. This is the lowest reported malignancy rate in a North American study to date, and significantly lower than the average malignancy rate (35%) reported in the literature. Invasive biopsy of all 18F-FDG positive thyroid incidentalomas, as recommended by some studies, is unwarranted and further research to determine optimal management is needed. There was no clinically useful SUVmax cut-off value to determine malignancy and PET/CT may not be a useful imaging modality to follow these patients conservatively.

This is a case of a 52-year-old woman who underwent a hysterectomy to treat a large uterine perivascular epithelioid cell tumor. She was followed with serial F-18 FDG PET/CT scans due to positive surgical margins and vascular invasion on pathology. Initial surveillance PET/CT performed 6 months post surgery was negative; however, a second surveillance PET/CT performed 12 months post surgery showed an intensely FDG-avid recurrence in the pelvic surgical site. The patient received local radiotherapy, 2 cycles of taxol and carboplatin, and was placed on imatinib mesylate (Gleevec). A final PET/CT performed 6 months after initiation of therapy showed rapidly disseminating metastatic disease and the patient died 1 month later. This rare report highlights a potentially new utility of F-18 FDG PET/CT for surveillance of recurrence of a malignant uterine perivascular epithelioid cell tumor, as well as for evaluation of response to therapy.

Myeloid sarcoma is a tumor formed by extramedullary accumulation of myeloblasts or immature myeloid cells. These tumors can develop in lymphoid organs, bone, skin, soft tissue, and other organs, and may precede or occur concurrently with acute myeloid leukemia. This is a case of a 42-year-old man who presented with a 2-week history of cough and shortness of breath on exertion. A computed tomography (CT) scan showed a large mediastinal mass and pericardial effusion. An F-18 fluorodeoxyglucose positron emission tomography-CT scan showed intense fluorodeoxyglucose (FDG) uptake in the mediastinal mass with invasion of the parietal pericardium. Biopsy of the mediastinal mass and pericardium revealed myeloid sarcoma. The pericardial effusion was drained and the patient was treated with high-dose cytosine arabinoside (HiDAC) chemotherapy. A follow-up positron emission tomography-CT was done 2 months after the last cycle, showing poor response to therapy and significant progression of disease with invasion through the anterior chest wall. Myeloid sarcoma can be added to the differential diagnosis of F-18 FDG avid anterior mediastinal masses, as well as F-18 FDG uptake in the pericardium.