False-Positive Axillary Lymph Nodes on FDG PET/CT Resulting From COVID-19 Immunization

Challenging Axillary Lymph Nodes on PET/CT in Cancer Patients throughout COVID-19 Vaccination Era

BACKGROUND

The unexpected detection of axillary lymphadenopathy (AxL) in cancer patients (pts) represents a real concern during the COVID-19 vaccination era. Benign reactions may take place after vaccine inoculation, which can mislead image interpretation in patients undergoing F-18-FDG, F-18-Choline, and Ga-68-DOTATOC PET/CT. They may also mimic loco-regional metastases or disease. We assessed PET/CT findings after COVID-19 first dose vaccination in cancer patients and the impact on their disease course management.

METHODS

We evaluated 333 patients undergoing PET/CT (257 F-18-FDG, 54 F-18-Choline, and 23 Ga-68 DOTATOC) scans after the first vaccination with mRNA vaccine (Pfizer-BioNTech) (study group; SG). The uptake index (SUVmax) of suspected AxL was defined as significant when the ratio was > 1.5 as compared to the contralateral lymph nodes. Besides, co-registered CT (Co-CT) features of target lymph nodes were evaluated. Nodes with aggregate imaging positivity were further investigated.

RESULTS

Overall, the prevalence of apparently positive lymph nodes on PET scans was 17.1% during the vaccination period. 107 pts of the same setting, who had undergone PET/CT before the COVID-19 pandemic, represented the control group (CG). Only 3 patients of CG showed reactive lymph nodes with a prevalence of 2.8% (p < 0.001 as compared to the vaccination period). 84.2% of SG patients exhibited benign characteristics on co-CT images and only 9 pts needed thorough appraisal.

CONCLUSION

The correct interpretation of images is crucial to avoid unnecessary treatments and invasive procedures in vaccinated cancer pts. A detailed anamnestic interview and the analysis of lymph nodes' CT characteristics, after performing PET/CT, may help to clear any misleading diagnosis.

Solitary Axillary Lymph Node Metastasis From Bladder Cancer Detected by FDG PET/CT

ABSTRACT

Solitary axillary lymph node metastasis from bladder cancer is rare. A 65-year-old woman with a history of bladder urothelial carcinoma presented to our hospital with an axillary mass. No abnormal lesion in FDG PET/CT was identified except a solitary soft tissue mass with significant FDG uptake in the right axilla. Puncture pathology of the mass confirmed the metastasis of differentiated urothelial carcinoma.

SARS-CoV-2 Affects Thyroid and Adrenal Glands: An 18F-FDG PET/CT Study

BACKGROUND

Since most endocrine glands express ACE-2 receptors and can be infected by SARS-CoV-2 virus, this retrospective multicentre observational study aims to assess the metabolic activity of thyroid and adrenal glands of COVID-19 patients by 18F-FDG PET/CT.

METHODS

We retrospectively evaluated the 18F-FDG PET/CT scans of COVID-19 patients admitted by three different centres, either in a low-intensity department or in the intensive care unit (ICU). A visual assessment and a semi-quantitative evaluation of areas of interest in thyroid and adrenal glands were performed by recording SUVmax and SUVmean. The 18F-FDG PET/CT uptake in COVID-19 patients was compared with those observed in normal age-matched controls.

RESULTS

Between March 2020 and March 2022, 33 patients from three different centres (twenty-eight patients in a low-intensity department and five patients in ICU), were studied by 18F-FDG PET/CT during active illness. Seven of them were also studied after clinical remission (3-6 months after disease onset). Thirty-six normal subjects were used as age-matched controls. In the thyroid gland, no statistically significant differences were observed between control subjects and COVID-19 patients at diagnosis. However, at the follow-up PET/CT study, we found a statistically higher SUVmax and SUVmean (p = 0.009 and p = 0.004, respectively) in the thyroid of COVID-19 patients. In adrenal glands, we observed lower SUVmax and SUVmean in COVID-19 patients at baseline compared to control subjects (p < 0.0001) and this finding did not normalize after clinical recovery (p = 0.0018 for SUVmax and p = 0.002 for SUV mean).

CONCLUSIONS

In our series, we observed persistent low 18F-FDG uptake in adrenal glands of patients at diagnosis of COVID-19 and after recovery, suggesting a chronic hypofunction. By contrast, thyroid uptake was comparable to normal subjects at disease onset, but after recovery, a subgroup of patients showed an increased metabolism, thus possibly suggesting the onset of an inflammatory thyroiditis. Our results should alert clinicians to investigate the pituitary-adrenal axis and thyroid functionality at the time of infection and to monitor them after recovery.

Urological Safety and COVID-19 Vaccinations

OBJECTIVE

To discuss the impact of COVID-19 vaccines on the urological field and to review the available data in the literature.

MATERIAL AND METHODS

All the related reports and original articles discussing COVID-19 vaccines and their impact on the urological field were searched in PubMed, Scopus, and Web of Science.

RESULTS

There are few published articles discussing the COVID-19 vaccine impact on urology. Vaccine safety was confirmed in this field as no major side effects were described. AKI (Acute Kidney Injury) was reported in selected populations. However, about 1% of the side effects was urological. Rare genital complications, low urinary tract symptoms, and occasional gross hematuria were reported. Fertility seems to be not impaired after vaccination. A potential misinterpretation of radiological findings in the oncological field has been reported.

CONCLUSIONS

In the literature, there are few studies regarding COVID-19 vaccines and their impact on the urological and andrological fields. We need more studies and extended follow-ups after repeated vaccinations in order to have more corroborating data particularly in selected populations, such as kidney transplant recipients and oncological patients.

COVID-19 vaccination simulating lymph node progression in a patient with prostate cancer

Several cases of cancer patients with 18-fluorodeoxyglucose (¹⁸FDG) Positron Emission Tomography/Computed Tomography (PET/CT) evidence of metabolically active axillary lymph nodes after COVID-19 vaccination have been described, creating a diagnostic dilemma and sometimes leading to further unnecessary examinations. A 62-year-old male, diagnosed with prostate cancer, treated with hormone-therapy and radiotherapy of the prostate 2 years before, underwent fluorine-18 choline (F-FCH) PET/CT for restaging purpose, less than 3 weeks after he had received the second dose of the Pfizer BioNTech-BNT162b2 mRNA COVID-19 vaccine. This exam showed an increased F-FCH uptake and an enlargement of the left axillary, paratracheal, para-aortic, subcarinal, and hilar bilateral lymph nodes. Fourteen weeks later, the patient underwent a new F-FCH PET-CT scan, displaying an almost complete regularization of the FCH uptake in all the previously involved regions. The patient was not treated after the first PET-CT scan, thus, the aforementioned PET/CT findings represented inflammatory vaccine-related lymph nodes. This case highlights the significance of knowing vaccination history to correctly interpret imaging findings and to avoid false-positive reports.

Bilateral Avid Axillary Nodes on FDG PET/CT Due to Concurrent Booster COVID-19 Immunization and Seasonal Influenza Vaccination

ABSTRACT

In an attempt to protect the high-risk demographic and reduce burden on health care systems, concomitant administration of COVID-19 and influenza vaccines has been recommended by health bodies. The ComFluCOV trial indicates this is well tolerated with no reduction in immune response to either vaccine. A 48-year-old woman with right oropharyngeal squamous cell carcinoma underwent postradiotherapy FDG PET/CT, which demonstrated complete metabolic response. Incidental avid bilateral axillary lymphadenopathy of benign configuration was noted and concluded to be reactive in response to recent Pfizer-BioNTech booster and influenza vaccination. This is expected to be seen more frequently over the coming months.

Lymphadenopathy Post‐COVID‐19 Vaccination with Increased FDG Uptake May Be Falsely Attributed to Oncological Disorders: A Systematic Review

Coronavirus disease 2019 (COVID‐19) has caused a global pandemic that continues to cause numerous deaths to date. Four vaccines have been approved by the Food and Drug Administration as of July 2021 to prevent the transmission of COVID‐19: Pfizer, Moderna, AstraZeneca, and Janssen. These vaccines have shown great efficacy and safety profile. One side effect that has been widely reported is post‐COVID‐19 vaccination lymphadenopathy. Due to the mimicry of the lymphadenopathy for metastases in some oncologic patients, there have been reports of patients who underwent biopsies that showed pathologic confirmation of benign reactive lymphadenopathy secondary to the COVID‐19 vaccine. Therefore, understanding the incidence of lymphadenopathy post‐COVID‐19 vaccinations will help guide radiologists and oncologists in their management of patients, both present oncologic patients, and patients with concerns over their newly presenting lymphadenopathy. A systematic literature search was performed using several databases to identify relevant studies that reported lymphadenopathy post‐COVID‐19 vaccination. Our results revealed that several cases have been detected in patients undergoing follow‐up fluorodeoxyglucose (FDG)‐positron emission tomography‐computerized tomography scans where lymph nodes ipsilateral to the vaccine injection site show increased uptake of FDG. Thus, knowledge of the incidence of lymphadenopathy may help avoid unnecessary biopsies, interventions, and changes in management for patients, especially oncologic patients who are at risk for malignancies.

Lymphadenopathy has been widely reported post‐COVID‐19 vaccination including patients undergoing follow‐up FDG‐PET‐CT scans which showed increased FDG uptake

Care must be taken before suspecting lymph node metastasis or deciding for lymphadenectomy following COVID‐19 vaccination

Hypermetabolic abdominal and cervical lymph nodes mimicking Hodgkin lymphoma relapse on FDG PET/CT after adenovirus-vectored COVID-19 vaccine

Vaccine-associated hypermetabolic lymphadenopathy (VAHL) has been reported as a common post-vaccination side effect, especially with mRNA-based COVID-19 vaccines. Most VAHL cases present normal or enlarged regional lymph nodes close to the injection site, usually with mild-moderate FDG (18 F-Fluorodeoxyglucose) uptake on FDG positron emission tomography (PET)/CT. Here, we describe the case of a 33-year-old woman with past history of Classic Hodgkin Lymphoma (CHL) who underwent follow-up FDG PET/CT 3 days (d) after the first dose of the adenovirus-vectored Oxford-AstraZeneca COVID-19 vaccine. FDG PET/CT showed unexpected small hypermetabolic cervical and abdominal lymph nodes in the same location as at the onset of the disease, suggesting radiological relapse. Considering temporal relationship and other cases of VAHL, a new image was performed 2 months later, which revealed decreased lymph nodes and normalization of FDG uptake. This case illustrates that the possibility of a false-positive should always be considered by physicians in this new context, even when hypermetabolic lymph nodes appear far from the vaccination site.

COVID-19 vaccination mimicking lymph-node progression in a patient with melanoma: a case report

COVID-19 vaccination has been rapidly implemented among patients with cancer. We present the case of a patient with high-risk resected cutaneous melanoma, who was a candidate for adjuvant treatment, with postsurgery 18-fluorodeoxyglucose (FDG) PET/computed tomography (CT) scan showing positive axillary lymph nodes after COVID-19 vaccination. This report presents a 50-year-old man with a history of stage IIA cutaneous melanoma. During follow-up, the patient experienced subcutaneous and lymph-node disease progression, documented with 18FDG PET/CT scan. The patient underwent laparoscopic left para-aortic lymphadenectomy and excision of subcutaneous lesion. Histologic examination showed presence of melanoma metastases in 2 lymph nodes out of total 17 excised and neoplastic emboli to the subcutaneous tissue. In view of starting adjuvant nivolumab, the patient underwent CT scan restaging, with evidence of suspect centimetric periaortic and paracaval lymph nodes, which were deemed worthy of 18FDG PET investigation. The 18FDG PET/CT was negative for abdominal hypercaptation, but showed left axillary pathologic lymph nodes. The medical history of the patient revealed that he had received intramuscular Moderna COVID-19 mRNA vaccine in the left deltoid, one week before 18FDG PET examination. Since the patient's clinical examination was negative and suspecting postvaccination false-positive adenopathy, bilateral axillary ultrasound was performed, excluding the presence of pathologic lymph nodes. The patient has started adjuvant treatment with nivolumab, which is currently ongoing. This case demonstrates unexpected findings in response to COVID-19 vaccination in a patient with melanoma. In this specific case, the detection of 18FDG PET hypercaptation could significantly change the patient's management. With growing evidence about the pattern and occurrence of adenopathies after mRNA COVID-19 vaccination, recommendations for scheduling and interpretation of 18FDG PET/CT scans among cancer patients will be implemented, in order to reduce equivocal findings and improve outcomes.

[18F]FDG uptake of axillary lymph nodes after COVID-19 vaccination in oncological PET/CT: frequency, intensity, and potential clinical impact

OBJECTIVES

To assess the frequency, intensity, and clinical impact of [¹⁸F]FDG-avidity of axillary lymph nodes after vaccination with COVID-19 vaccines BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) in patients referred for oncological FDG PET/CT.

METHODS

One hundred forty patients referred for FDG PET/CT during February and March 2021 after first or second vaccination with Pfizer-BioNTech or Moderna were retrospectively included. FDG-avidity of ipsilateral axillary lymph nodes was measured and compared. Assuming no knowledge of prior vaccination, metastatic risk was analyzed by two readers and the clinical impact was evaluated.

RESULTS

FDG PET/CT showed FDG-avid lymph nodes ipsilateral to the vaccine injection in 75/140 (54%) patients with a mean SUV_max of 5.1 (range 2.0 - 17.3). FDG-avid lymph nodes were more frequent in patients vaccinated with Moderna than Pfizer-BioNTech (36/50 [72%] vs. 39/90 [43%] cases, p < 0.001). Metastatic risk of unilateral FDG-avid axillary lymph nodes was rated unlikely in 52/140 (37%), potential in 15/140 (11%), and likely in 8/140 (6%) cases. Clinical management was affected in 17/140 (12%) cases.

CONCLUSIONS

FDG-avid axillary lymph nodes are common after COVID-19 vaccination. The avidity of lymph nodes is more frequent in Moderna compared to that in Pfizer-BioNTech vaccines. To avoid relatively frequent clinical dilemmas, we recommend carefully taking the history for prior vaccination in patients undergoing FDG PET/CT and administering the vaccine contralateral to primary cancer.

KEY POINTS

• PET/CT showed FDG-avid axillary lymph nodes ipsilateral to the vaccine injection site in 54% of 140 oncological patients after COVID-19 vaccination. • FDG-avid lymphadenopathy was observed significantly more frequently in Moderna compared to patients receiving Pfizer-BioNTech-vaccines. • Patients should be screened for prior COVID-19 vaccination before undergoing PET/CT to enable individually tailored recommendations for clinical management.