Subdiaphragmatic Lymph Nodes Uptake on 18F-FDG PET/CT After COVID-19 Vaccination in the Thigh

Widespread Reactive Lymphatic and Splenic FDG Avidity After mRNA COVID Vaccination

ABSTRACT

A 75-year-old woman with history of metastatic lung adenocarcinoma in remission develops new widespread FDG-avid lymphadenopathy in the neck, chest, abdomen, and pelvis on surveillance PET/CT, as well as intense FDG uptake in the spleen, without evidence of local recurrence. Short-term follow-up PET demonstrates near-complete resolution of FDG-avid lymphatic and splenic FDG avidity without interval change in management. Further history reveals that the patient received her fifth dose of COVID mRNA vaccine 6 days before the abnormal PET. Although unilateral axillary adenopathy after COVID vaccination is well-recognized, this widespread symmetric lymphatic and splenic FDG avidity is a significantly rarer phenomenon.

COVID-19: Findings in nuclear medicine from head to toe

COVID-19 is a multisystemic disease, and hence its potential manifestations on nuclear medicine imaging can extend beyond the lung. Therefore, it is important for the nuclear medicine physician to recognize these manifestations in the clinic. While FDG-PET/CT is not indicated routinely in COVID-19 evaluation, its unique capability to provide a functional and anatomical assessment of the entire body means that it can be a powerful tool to monitor acute, subacute, and long-term effects of COVID-19. Single-photon scintigraphy is routinely used to assess conditions such as pulmonary embolism, cardiac ischemia, and thyroiditis, and COVID-19 may present in these studies. The most common nuclear imaging finding of COVID-19 vaccination to date is hypermetabolic axillary lymphadenopathy. This may pose important diagnostic and management dilemmas in oncologic patients, particularly those with malignancies where the axilla constitutes a lymphatic drainage area. This article aims to summarize the relevant literature published since the beginning of the pandemic on the intersection between COVID-19 and nuclear medicine.

The Onset of Sarcoidosis After COVID-19 Vaccination Revealed by the 18 F-FDG PET

ABSTRACT

Sarcoidosis is a heterogeneous multisystem disease characterized by noncaseating granulomas. We presented 18 F-FDG PET/CT findings of sarcoidosis in a previously healthy 43-year-old man who presented intermittent cough after the third dose of COVID-19 vaccination. 18 F-FDG PET/CT showed high uptake of one solitary nodule in the right middle lobe, mediastinal lymph nodes, bilateral hila, and multiple nodules under the right pleura, mimicking the malignancy. Nevertheless, the biopsy confirmed distinct noncaseating granulomas. This case emphasizes the onset of sarcoidosis revealed by 18 F-FDG PET/CT after COVID-19 vaccination.

Understanding COVID Vaccination and Its Implication in Cancer Patients’ Imaging of Lymph Nodes by PET-CT

(1) Background: The appearance of enlarged lymph nodes on imaging adds another layer of complexity to the differential diagnosis of disease progression versus immune response to COVID-19 vaccines. Our aim was to find an optimal timing between the vaccination and the PET-CT scan. (2) Methods: 25 cancer patients with ¹⁸F-FDG PET-CT evaluations and a history of COVID-19 vaccination between September 2021 and December 2021 were retrospectively analyzed to characterize the lymph nodes related to the time interval from COVID vaccination. (3) Results: All patients presented one or more adenopathies localized in the ipsilateral axilla (96%), ipsilateral cervical area (20%), ipsilateral retropectoral (20%) and pulmonary hilum (8%). The median value of SUVmax was 3.5 ± 0.5. There was a significant indirect correlation between SUVmax and the time passed between the vaccination and the PET CT (Pearson Correlation r = −0.54, p = 0.005). There was no significant difference (p = 0.19) in the SUVmax value in patients receiving Moderna mRNA-1273 vaccine vs. BNT162b2 mRNA Pfizer vaccine. (4) Conclusions: Lymph node enlargement is commonly seen in patients post-vaccination for COVID-19 and must be differentiated from disease progression. The data from our study strongly suggests that the minimum interval of time between an mRNA vaccine and a PET-CT should be more than six weeks.