COVID-19 mRNA vaccination-induced lymphadenopathy mimics lung cancer metastasis on fluorodeoxyglucose PET/CT scan

Yukihiro Hama; Etsuko Tate

doi:10.4103/2588-9044.338635

CASE REPORT

Year : 2021 | Volume : 5 | Issue : 4 | Page : 165-167

COVID-19 mRNA vaccination-induced lymphadenopathy mimics lung cancer metastasis on fluorodeoxyglucose PET/CT scan

Yukihiro Hama, Etsuko Tate
Department of Radiology and Radiation Oncology, Edogawa Hospital, Edogawa-Ku, Tokyo, Japan

Date of Submission	25-Dec-2021
Date of Acceptance	29-Dec-2021
Date of Web Publication	28-Feb-2022

Correspondence Address:
Dr. Yukihiro Hama
Department of Radiology and Radiation Oncology, Edogawa Hospital, 2-24-18 Higashikoiwa, Edogawa-Ku, Tokyo 133-0052
Japan

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2588-9044.338635

Abstract

A 66-year-old man with stage IIA nonsmall cell lung cancer who had complete response to radiation therapy 4.5 years earlier underwent a fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) scan due to elevated CA19-9 levels. PET/CT scan showed a new cluster of left axillary and supraclavicular lymphadenopathy with increased FDG uptake suggesting lymph node metastasis. Later, it was found that the patient received the second dose of coronavirus disease 2019 mRNA vaccine 7 days before the PET/CT. Retrospective evaluation showed a vague linear-shaped metabolic activity in the left deltoid muscle with mild FDG uptake in the injection site. Based on the detailed history and PET/CT findings, a diagnosis of vaccination-induced lymphadenopathy was made. This diagnosis was confirmed after 6 months of follow-up.

Keywords: Immunity, nonsmall-cell lung carcinoma, radiation therapy, SARS-CoV-2, vaccination

How to cite this article:
Hama Y, Tate E. COVID-19 mRNA vaccination-induced lymphadenopathy mimics lung cancer metastasis on fluorodeoxyglucose PET/CT scan. Libyan J Med Sci 2021;5:165-7

How to cite this URL:
Hama Y, Tate E. COVID-19 mRNA vaccination-induced lymphadenopathy mimics lung cancer metastasis on fluorodeoxyglucose PET/CT scan. Libyan J Med Sci [serial online] 2021 [cited 2023 Mar 27];5:165-7. Available from: https://www.ljmsonline.com/text.asp?2021/5/4/165/338635

Introduction

A nationwide vaccination using mRNA vaccines against coronavirus disease 2019 (COVID-19) has been done in Japan. There are two vaccines available, one made by Pfizer-BioNTech (BNT162b2 mRNA COVID-19 Vaccine)^[1] and the other by Moderna (mRNA-1273 SARS-CoV-2 Vaccine),^[2] both of which have been reported to have side effects of axillary and supraclavicular lymphadenopathy. When postvaccinated oncologic patients underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) scans, differentiation between the malignant and benign nature of the hypermetabolic lymphadenopathy could be difficult.^[3],[4] FDG uptake at the injection site is one of the diagnostic clues for vaccine-associated hypermetabolic lymphadenopathy.^[5] However, FDG uptake at the injection site is not always present and can be obscured, making it difficult to differentiate between benign and malignant lesions. Here, we report a case of lung cancer in which axillary and supraclavicular lymph node metastasis was suspected after radical radiation therapy and later diagnosed as vaccine-associated hypermetabolic lymphadenopathy.

Case Report

A 66-year-old Japanese man who had undergone definitive radiation therapy for stage IIA nonsmall cell lung cancer (NSCLC) visited our hospital for regular follow-up. He received intensity-modulated radiotherapy (IMRT) for localized lung adenocarcinoma of the right upper lobe (cT2b, N0, M0, Stage IIA, AJCC, 8e) 4½ years ago. He refused chemotherapy and has been followed up without any adjuvant treatment. Whole-body FDG PET/CT before IMRT showed no lymph node metastasis or distant metastasis [Figure 1]a, [Figure 1]b, [Figure 1]c. Six months after IMRT, the lung cancer disappeared, and subsequent follow-up CT showed no recurrence [Figure 1]d. However, 4½ years after IMRT, the serum CA19-9 was elevated from 42.8 U/ml to 433.4 U/ml (normal <37 U/mL) within 6 months; FDG PET/CT scan was performed to assess the recurrence of NSCLC or the presence of another malignant tumor. Whole-body FDG PET/CT scan showed a new cluster of left axillary and supraclavicular lymphadenopathy with increased FDG uptake [Figure 1]e. The radiologists in charge diagnosed the left axillary and supraclavicular lymphadenopathy with increased FDG uptake as lymph node metastasis. Later, it was found that the patient received the first dose of Pfizer-BioNTech COVID-19 vaccine 28 days before the PET/CT, and the second dose at 7 days before the PET/CT. Retrospective evaluation of the PET/CT showed a vague linear-shaped metabolic activity in the left deltoid muscle with mild FDG uptake in the injection site [Figure 1]e. These findings were suspected to be due to recent vaccinations rather than metastasis. Whole-body CT scans were taken every 3 months, and serum CA19-9 levels were also measured. The size of left axillary and supraclavicular lymph nodes did not change for 6 months after a relapse was suspected, and the serum CA19-9 level gradually decreased without treatment during the follow-up period. Based on the PET/CT findings and 6-month follow-up results, the abnormal uptake in the left axillary and supraclavicular lymph nodes was diagnosed as vaccine-associated hypermetabolic lymphadenopathy. At a follow-up of 5.5 years after IMRT, there is no recurrence of NSCLC.

Figure 1: Chest computed tomography and 18F-fluorodeoxyglucose positron emission tomography/computed tomography images. (a) Chest computed tomography scan showing a 4.8 cm spiculated mass (arrow) in the right upper lobe with suspicious local extension to the pleura. (b) Fused positron emission tomography/computed tomography image showing a hypermetabolic pulmonary mass (arrow) in the right upper lobe. (c) Maximum intensity projection of fluorodeoxyglucose positron emission tomography images demonstrating a hypermetabolic lesion in the right lung. (d) Chest computed tomography scan 4½ years after radiotherapy showing that the lung cancer has disappeared and there is no local recurrence. (e) Maximum intensity projection of fluorodeoxyglucose positron emission tomography images 4½ years after radiotherapy showing a new cluster of left axillary and supraclavicular lymphadenopathy with increased fluorodeoxyglucose uptake (arrowheads). Later, retrospective evaluation showing a linear-shaped metabolic activity in the left deltoid muscle and the injection site (arrows)

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Discussion

This case report shows important precautions for performing a PET/CT scan when cancer recurrence is suspected after radiation therapy. If the patient's tumor marker increases during the follow-up period and CT is inconclusive, FDG PET/CT scan is a reasonable imaging test to scrutinize for recurrence. Since vaccination has only recently become available, a detailed questionnaire regarding vaccination may not be conducted before the PET/CT scan. This report indicates the importance of asking about COVID-19 mRNA vaccination before the PET/CT scan. FDG uptake into lymph nodes tends to occur within 7 days after vaccination and generally disappears within 12–14 days but may remain for 4–10 weeks.^[6] This patient received the second dose of Pfizer-BioNTech COVID-19 vaccine 7 days before the PET/CT, and abnormal accumulation of FDG was observed in the left axillary and supraclavicular lymph nodes. It is acceptable to postpone the PET/CT scan to avoid false-positive findings, but it should be done as planned in an oncologic patient because of the risk of the delay adversely affecting the cancer treatment.^[5] This case report suggests that PET/CT can be accurately interpreted by conducting a detailed history regarding vaccination and recognizing FDG accumulation at the injection site.

There are several limitations that should be addressed in this report. First, the timing of FDG PET/CT scan was not optimal. We consider that PET/CT should not have been performed for at least 2 weeks after vaccination.^[7] However, if recurrence is strongly suspected, the disadvantage of delaying the PET/CT scan should be fully considered. Second, information on the patient questionnaire, including date and site of previous vaccinations, was not available at the time of PET/CT scan. If detailed information about the vaccination had been obtained before the PET/CT scan, the abnormal FDG accumulation may have been correctly diagnosed. As of now, due to the lack of scientific evidence and guideline, an institutional approach to cancer patients receiving FDG PET/CT scans after COVID-19 vaccination is needed.^[6],[7]

Conclusion

In conclusion, the results of this single case report cannot be generalized to others without further investigations; however, asking detailed questions about vaccinations, optimizing the timing of PET/CT scans, and recognizing characteristic findings on PET/CT images may improve the accuracy of the interpretation.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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