newhypermetabolic liver metastases (SUVmax 13.4); new diffuse increased uptake was seen in the spleen (SUVmax 4.7) without splenomegaly together with focal moderate FDG uptake in the left deltoid muscle (SUVmax 2.8), at the site of recent COVID-19 vaccine; new FDG uptake in multi-station lymph nodes above and below the diaphragm including prominent upper abdominal lymph nodes (SUVmax up to 6.4)/ persistently increased uptake in cervical, thoracic, and abdominopelvic lymph nodes; This literature-non-study case was reported in a literature article and describes the occurrence of METASTASES TO LIVER (newhypermetabolic liver metastases (SUVmax 13.4)) in a 73-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.   Concurrent medical conditions included Adenocarcinoma of the gastroesophageal junction stage IV and Metastatic liver carcinoma. Concomitant products included FLUOROURACIL, FOLINIC ACID, OXALIPLATIN (FOLFOX), REGORAFENIB and NIVOLUMAB for Adenocarcinoma of the gastroesophageal junction stage IV and Metastatic liver carcinoma.   In January 2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. In February 2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In August 2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In October 2021, the patient experienced SPLEEN FOLLICULAR HYPERPLASIA (new diffuse increased uptake was seen in the spleen (SUVmax 4.7) without splenomegaly together with focal moderate FDG uptake in the left deltoid muscle (SUVmax 2.8), at the site of recent COVID-19 vaccine) and LYMPHADENOPATHY (new FDG uptake in multi-station lymph nodes above and below the diaphragm including prominent upper abdominal lymph nodes (SUVmax up to 6.4)/ persistently increased uptake in cervical, thoracic, and abdominopelvic lymph nodes). In February 2022, the patient experienced METASTASES TO LIVER (newhypermetabolic liver metastases (SUVmax 13.4)) (seriousness criterion medically significant). In May 2022, SPLEEN FOLLICULAR HYPERPLASIA (new diffuse increased uptake was seen in the spleen (SUVmax 4.7) without splenomegaly together with focal moderate FDG uptake in the left deltoid muscle (SUVmax 2.8), at the site of recent COVID-19 vaccine) and LYMPHADENOPATHY (new FDG uptake in multi-station lymph nodes above and below the diaphragm including prominent upper abdominal lymph nodes (SUVmax up to 6.4)/ persistently increased uptake in cervical, thoracic, and abdominopelvic lymph nodes) had resolved. At the time of the report, METASTASES TO LIVER (newhypermetabolic liver metastases (SUVmax 13.4)) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In June 2021, Positron emission tomogram: a hypermetabolic malignant mass in distal esophagus (SUVmax 20.5), liver metastases (SUVmax up to 6.0), and a hypermetabolic nodular lesion (SUVmax 3.9), probably malignant implant, at the interface of stomach and transverse colon.. In October 2021, Positron emission tomogram: approximately 8 weeks following booster dose of COVID-19 vaccine. The scan showed decreased or resolved FDG uptake in distal esophageal lesion, hepatic metastases and at gastric/colonic wall while development of new FDG uptake in multi-station lymph nodes above and below the diaphragm including prominent upper abdominal lymph nodes (SUVmax up to 6.4). In addition, new diffuse increased uptake was seen in the spleen (SUVmax 4.7) without splenomegaly together with focal moderate FDG uptake in the left deltoid muscle (SUVmax 2.8), at the site of recent COVID-19 vaccine.. In December 2021, Positron emission tomogram: approximately 16 weeks after booster dose of COVID-19 vac- cine demonstrated persistently increased uptake in cervical (SUVmax 5.0), thoracic (SUVmax 3.5), and abdominopelvic (SUVmax 7.4) lymph nodes, as well as diffuse splenic (SUV 5.4) uptake without evidence for active malignancy.. In February 2022, Positron emission tomogram: approximately 23 weeks following booster dose of COVID-19 vaccine, showed new hypermetabolic liver metastases (SUVmax 13.4), however decreased FDG uptake in mediastinal (SUVmax 2.1), and abdominopelvic (SUVmax 4.5) lymph nodes and decreased uptake in spleen (SUVmax 3.2), further supporting the reactive etiology while excluding lymphomatous disease process.. In May 2022, Positron emission tomogram: approximately 34 weeks following booster dose of COVID-19 vaccine, decreased FDG avid hepatic (SUVmax 3.1) metastases while resolved reac- tive FDG activity in neck, thoracic, and abdominopelvic lymph nodes as well as diffuse splenic FDG uptake was observed.. On an unknown date, Computerised tomogram: FDG avid lymph nodes were benign appearing.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered SPLEEN FOLLICULAR HYPERPLASIA (new diffuse increased uptake was seen in the spleen (SUVmax 4.7) without splenomegaly together with focal moderate FDG uptake in the left deltoid muscle (SUVmax 2.8), at the site of recent COVID-19 vaccine) and LYMPHADENOPATHY (new FDG uptake in multi-station lymph nodes above and below the diaphragm including prominent upper abdominal lymph nodes (SUVmax up to 6.4)/ persistently increased uptake in cervical, thoracic, and abdominopelvic lymph nodes) to be related. No further causality assessment was provided for METASTASES TO LIVER (newhypermetabolic liver metastases (SUVmax 13.4)).    It was reported that patient was started within a research protocol on folfox, regorafenib, and nivolumab from June 2021 onwards. However, because of nivolumab related acute interstitial nephritis, patient was continued on folfox and regorafenib only. No granulocyte-macrophage colony-stimulating factors (GM-CSF) was administered at any time in the course of therapy.   The constellation of findings along with history of recent vaccination indicated a vaccine-related generalized immune activation.  Patient developed increase metabolic activity in spleen and benign appearing lymph nodes at several location probably indicating generalized immune response after a booster dose of Moderna COVID-19 vaccine.  In conclusion reported that COVID-19 vaccinations could have relevant implications on F- FDG PET/CT scan interpretation in cancer patients potentially leading to false positive findings particularly in cases of prolonged generalized immune response. This rare but important manifestation could present as multi-station hypermetabolic reactive lymph nodes and diffuse splenic uptake up to 8 months following the vaccination. Therefore, F-FDG PET/CT scans should be interpreted with caution in patients with COVID-19 vaccines.  No treatment medication information was reported.  Company comment: This literature non study case concerns a 73-year-old, male patient with medical history of EGD cancer stage IV, with liver metastases, who experienced the unexpected serious (medically significant) event of metastases to liver (new metastases to liver) and non serious events of lymphadenopathy and spleen follicular hyperplasia. The events of lymphadenopathy and spleen follicular hyperplasia occurred approx. 2 months after the third dose of mRNA-1273., while new liver metastases were observed 6 months after 3rd dose. As reported, new diffuse increased uptake was seen in the spleen (SUVmax 4.7) without splenomegaly together with focal moderate FDG uptake in the left deltoid muscle (SUVmax 2.8), at the site of recent COVID-19 vaccine) also new FDG uptake in multi-station lymph nodes above and below the diaphragm including prominent upper abdominal lymph nodes (SUVmax up to 6.4)/ and persistently increased uptake in cervical, thoracic, and abdominopelvic lymph nodes was observed. Authors discussed that prolonged immunological response occurred in patient following COVID 19 vaccination increasing the FDG uptake and making it difficult to differentiate between ne onset or spread of disease and benign immunological response triggered by COVID 19 vaccination. Considering the stage of patient's disease with already present liver metastases and tendency of further expansion as natural course of malignant disease causality for new liver metastases is assessed as not related. The benefit-risk relationship of mRNA-1273 is not affected by this report.    Most recent FOLLOW-UP information incorporated above includes: On 09-Jun-2023: Live follow up received by safety on 09-Jun-2023 has Email with FTA received and contains significant information: literature details, reporter information, patient history, concomitant medications, suspect details, events and narrative updated.