SUVmax of 5.3 and left axillary nodes measuring up to 8 mm with SUVmax of 4.4 concerning for metastatic disease; This is a literature report.  A 64-year-old male patient received BNT162b2 (BNT162B2), as dose 3 (booster), single (Batch/Lot number: unknown) for covid-19 immunisation. The patient's relevant medical history included: "chronic obstructive pulmonary disease" (unspecified if ongoing); "former smoker" (unspecified if ongoing), notes: 20-pack-year smoking history; "lung adenocarcinoma" (unspecified if ongoing). The patient's concomitant medications were not reported. Vaccination history included: Covid-19 vaccine (Dose 1), for Covid-19 Immunisation; Covid-19 vaccine (Dose 2), for Covid-19 Immunisation. The following information was reported: LYMPHADENOPATHY (hospitalization, medically significant), outcome "recovered", described as "SUVmax of 5.3 and left axillary nodes measuring up to 8 mm with SUVmax of 4.4 concerning for metastatic disease". The patient underwent the following laboratory tests and procedures: Computerised tomogram thorax: found to have a 1.7 cm solid nodule, notes: in the left upper lobe with irregular margins on low dose; Histology: consistent with the diagnosis of adenocarcinoma; maximum standardized uptake value: 5.3 and left axillary nodes measuring up to 8 mm; 4.4 concerning for metastatic disease; Positron emission tomogram: showed a 16 mm nodule in the pulmonary lobe; resolution of axillary lymphadenopathy, notes: four weeks later. Therapeutic measures were taken as a result of lymphadenopathy.  INTRODUCTION: The Coronavirus disease 2019 (COVID-19) pandemic affected millions of people globally, prompting the emergent need for an effective vaccine. Lymphadenopathy associated with COVID-19 vaccine is a recognized phenomenon that can present a diagnostic dilemma for staging thoracic malignancies. We present a case of post COVID-19 vaccination axillary lymphadenopathy complicating the staging process for a patient with newly diagnosed lung adenocarcinoma.  CASE PRESENTATION: A 64-year-old male with chronic obstructive pulmonary disease, former smoker with a 20-pack-year smoking history was found to have a 1.7 cm solid nodule in the left upper lobe with irregular margins on low dose computed tomography (CT) scan of the chest for lung cancer screening. Fine needle aspiration of the nodule was done, and histopathology results were consistent with the diagnosis of adenocarcinoma. Patient then underwent fluorodeoxyglucose-positron emission tomography (FDG-PET) scan that showed a 16 mm nodule in the left upper pulmonary lobe with maximum standardized uptake value (SUVmax) of 5.3 and left axillary nodes measuring up to 8 mm with SUVmax of 4.4 concerning for metastatic disease. On further history, patient had received the Pfizer mRNA vaccination booster three days prior to undergoing the FDG-PET scan. Patient was evaluated by oncology and decision was made to treat with a 7-day course of prednisone 20 mg daily and to repeat FDG-PET scan. FDG-PET scan done four weeks later showed resolution of axillary lymphadenopathy. Patient was clinically staged as T1bN0M0 stage 1A and underwent robotic left upper lobe lingular-sparing lobectomy.  DISCUSSION: In patients with thoracic malignancies, lymphadenopathy related to COVID-19 vaccination with avid FDG uptake on PET scan was reported in 29% of patients (2). The presentation of FDG avid lymphadenopathy creates a clinical challenge by confounding accurate cancer staging and leading to unnecessary workup (3). More importantly, detection of lymphadenopathy while staging lung cancer has crucial implications in the process of triaging patients to oncologic management in terms of candidacy for surgical resection (3). Currently, no consensus is available to guide management for incidental lymphadenopathy associated with COVID-19 vaccination in lung cancer patients. For this patient, we chose to treat with steroids and to obtain repeat imaging within 4 weeks of the original FDG-PET to not delay treatment planning. Repeat imaging showed resolution of the axillary lymphadenopathy and patient was able to undergo definitive treatment promptly.  CONCLUSION(S): This case highlights the diagnostic challenge posed by COVID-19 lymphadenopathy in patients with newly diagnosed lung cancer and delineates our approach to navigating this challenge to avoid malignancy up-staging and treatment delay.; Sender's Comments: Based on the current available limited information in the case provided, the causal association between the events and the use of suspect product BNT162B2 cannot be fully excluded. The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.