Short Report
Mild SARS-CoV-2 infection with the Omicron variant mimicking metastatic cancer on whole body 18-F FDG PET/CT imaging
https://doi.org/10.21203/rs.3.rs-4009720/v1
This work is licensed under a CC BY 4.0 License
posted
You are reading this latest preprint version
We present a case with unusual findings on nuclear imaging after mild SARS-CoV-2 infection. 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography showed activity in the lower thoracic spinal column, in portal lymph nodes, and in the terminal ileum and surrounding lymph nodes, all suspicious for metastatic cancer. Three months later, the findings had either disappeared or were considered reactive.
18-F FDG PET/CT
COVID-19
SARS-CoV-2
Omicron
spinal column
ileum
inflammation
metastatic disease
Coronavirus disease 2019 (COVID-19) is a multisystemic viral disease that to this date has infected most of the world’s population (1). Most people experience only mild symptoms, mainly from the respiratory system, but symptoms such as headache, loss of smell or taste, diarrhea, and muscle or joint pain are well-known (2). Some, especially people with risk factors such as high age or impaired immunity, have an increased risk of a severe course of disease including admittance to hospital and life-threatening pneumonia or multisystem disease (3). Also, some have symptoms lasting for months or even years, so-called Long COVID or post-acute sequelae of COVID-19 (PASC) (4).
Medical imaging has mainly shown findings in the lungs and upper respiratory lymph nodes in the acute phase, but these findings can also be present in the post-acute phase in which the ground-glass opacities are the most prevalent (5). Infection with SARS-CoV-2 has also been seen with medical imaging in other organs, but these findings are not as common (6). Here we present a mild case of COVID-19 with the Omicron variant presumably mimicking metastatic disease on 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography (FDG PET/CT) in a patient evaluated originally for an incidentaloma.
A 77-year-old woman was evaluated at a dermatology department for chronic pruritus during winter 2022–2023. She was a former smoker (10 pack years), overweight (BMI 33) and received medication for paroxysmic atrial fibrillation (anti-coagulant), hypercholesterolemia, and hypertension. Blood samples showed an elevated Fibrosis-4 (FIB-4) Index for Liver Fibrosis (an index for cirrhosis based on aspartate transaminase, alanine transaminase, platelet count, and age). She was referred for a normal liver ultrasound, yet identified an incidental finding showing a process near the right atrium that was confirmed with echocardiography. In February 2023, she was referred to a secondary hospital for evaluation of myxoma. Magnetic resonance imaging (MRI) of the heart localised the myxoma behind the atrium and was therefore considered benign. However, later in the diagnostic work-up an FDG PET/CT scan was performed which showed increased focal uptake in the right thyroid gland, the spinal column (vertebra Th10), in portal lymph nodes, the terminal ileum, and surrounding lymph nodes. Figure 1 shows the whole-body projection of FDG PET/CT and Fig. 2 shows trans axial slices of fused FDG PET/CT at three localisations. Extensive blood samples were taken, including immunologic and rheumatologic markers which showed normal hematologic markers except for a slight increase in the monoclonal bands (M-component). Due to the suspicion of advanced malignant disease, a hunt for the primary tumor was initiated. Biopsy specimens were taken from the thyroid gland, the spinal column, and the terminal ileum. Due to the elevated M-component in the blood samples, whole-body low-dose multidetector-row CT in multiple myeloma, spinal magnetic resonance (MR) for myeloma, and bone marrow biopsy were performed to examine for neoplastic proliferation of monoclonal plasma cells within the bone marrow. These examinations showed no signs of malignancy, only slight signs of inflammation such as lymphocyte aggregation. The mammography was normal. In June 2023, thyroid scintigraphy (99m-Tc-pertechnetate) showed a hypo-functioning area corresponding to the site of activity in the FDG PET/CT. The ultrasonic re-examination revealed a normally sized thyroid with benign nodules, some showing calcifications, notably in the left lobe. In the isthmus, a 7 x 6 mm (about 0.24 in) hypoechoic alteration with coarse calcification was observed. A small 5 x 5 x 5 mm (about 0.2 in) hypoechoic nodule with abundant Doppler signals was also present nearby. FDG PET/CT suggested the most intense signal came from the hypoechoic area; a fine-needle aspiration (FNA) was conducted from the mentioned 5 mm nodule with no immediate complications. However, the FNA was inconclusive due to a lack of material.
Three months later, in July 2023, the FDG PET/CT was repeated (Figs. 1 and 2). Now, the previous findings had mostly resolved – completely in the terminal ileum and surrounding lymph nodes - and otherwise lowered significantly to a reactive or benign level. The only exception was the thyroid gland, in which a repeated biopsy indicated a very low-risk papillary thyroid adenocarcinoma (T1aN0M0) for which she had a successful total thyroidectomy in September 2023.
In October 2023, the woman recalled having had a mild SARS-CoV-2 infection seven days before the first FDG PET/CT was performed but reported having recovered fully at the time of the scan. The infection was diagnosed with a lateral flow test, and she received no medical treatment. She was triple-vaccinated against SARS-CoV-2, with an mRNA-based vaccination (Comirnaty) in 2021 but had not received a booster for the winter season 2022.
The present case story involved numerous PET-positive areas mimicking cancer during COVID-19 disease. However, it also revealed a very low-risk papillary thyroid adenocarcinoma, prompting a successful thyroidectomy. SARS-CoV-2 infection is known to affect the results of medical imaging; this influence has predominantly been observed in cases involving the more pathogenic variants before the Omicron variant. The most common findings have been seen in the lungs and upper respiratory lymph nodes (5), but diffuse activity has also been seen in other organs (6). Also, changes in imaging have been observed following COVID-19 vaccination, especially in the regional lymph nodes of the area of vaccination (7). This has interfered with the evaluation of oncologic patients (8–10), especially where pulmonary metastases have been suspected.
If the case was different, i.e. without the excessive FDG PET/CT changes, one might have considered monitoring the very low-risk papillary thyroid adenocarcinoma, given the positive outcomes. Active surveillance has been increasingly embraced globally as an alternative to immediate surgery (11). To this day, we have not yet found comparable results to our findings in the literature, where COVID-19 increases FDG activity at such a high local level in extra-pulmonary areas, hence mimicking metastatic cancer.
These findings could contribute to the understanding of post-acute COVID-19, but it is equally important to evaluate whether imaging should be postponed if the patient has had recent infectious diseases such as COVID-19, or at least interpreted with caution, when performing oncologic assessment, as these findings could be misinterpreted, preventing unnecessary examinations, invasive procedures such as biopsies, excessive radiation exposure from repeated CT scans and PET/CT, and, in extreme cases, unwarranted surgeries.
Funding
The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.
Competing Interests
The authors have no relevant financial or non-financial interests to disclose.
Author Contributions
Herborg L Johannesen and Gunnhild Helmsdal conceptualised and collected the data material for the study. Gunnhild Helmsdal drafted and wrote the original manuscript. Gunnhild Helmsdal, Sissal Clemmensen, Jann Mortensen, Marnar Fríðheim Kristiansen, Maria Skaalum Petersen and Herborg L Johannesen commented, edited, wrote and accepted the final manuscript.
Data Availability
Some of the data and images presented and analysed during the current study are not publicly available as they have been collected from hospital journals and imaging systems but are available from the corresponding author on reasonable request.
Ethics Approval
The local Research Ethics Committee confirmed that the study did not require ethical approval.
Consent to Participate
The patient provided written consent to participate in the study.
Consent to Publish
The patient provided written consent for the data and images to be published.
No competing interests reported.
posted
You are reading this latest preprint version