Detection of Unilateral Axillary Nodal Uptake Both at ⁶⁸Ga-DOTATOC and ¹⁸F-FDG PET/CT After 1 Week From COVID-19 Vaccine

Abstract

Recently, vaccination against COVID-19 has gained wide diffusion, especially among vulnerable individuals, such as cancer patients. At the same time, patients have been undergoing PET/CT examinations after vaccination in an increasing number, and cases of false-positive axillary nodal uptake have been described, mostly at ¹⁸F-FDG PET. Here, we describe the case of both ⁶⁸Ga-DOTATOC and ¹⁸F-FDG axillary nodal uptake in a young woman affected by a metastatic retroperitoneal paraganglioma.

FIGURE 1.

We describe the case of a 29-year-old woman with stage IV retroperitoneal paraganglioma and disseminated bone metastases, who underwent both ⁶⁸Ga-DOTATOC and ¹⁸F-FDG PET/CT during her follow-up. After the injection of 101 MBq of ⁶⁸Ga-DOTATOC, the PET/CT examination revealed a stable disease in the already known numerous bone and pulmonary metastases; furthermore, a mild uptake was demonstrated in some small left axillary nodes (white and black arrows; A, MIP; B, axial PET image; C, CT image; D, fused PET/CT image). The day after, she underwent ¹⁸F-FDG PET/CT confirming bone and lung lesions and a mild uptake (SUV_max, 3.80) in the left axillary region, corresponding to the small nodes with fatty hilus previously observed (white and black arrows; E, axial PET image; F, CT image; G, fused PET/CT image; H, MIP). A fade uptake was also detected within the subcutaneous soft tissues superficial to the left deltoid muscle. The patient presented a history of receiving the Pfizer-BioNTech COVID-19 vaccine in the left deltoid muscle 6 and 7 days before the ⁶⁸Ga-DOTATOC and the ¹⁸F-FDG PET/CT, respectively. Tracer injection was via the right (contralateral) antecubital fossa in both examinations, hence not a potential cause. Clinical correlation and its morphological aspect supported the nodal uptake to be reactive, ascribed to the recent vaccination. Similar findings were described after COVID-19 vaccinations (both Pfizer-BioNTech and AZ) on ¹⁸F-FDG PET/CT^1–7 and, recently, also on ¹⁸F-choline PET/CT examination.⁸ To the best of our knowledge, this is the first case of a COVID-19 vaccine–related nodal uptake on ⁶⁸Ga-DOTATOC PET/CT, as very recently another case involving ⁶⁸Ga-DOTATATE PET/CT had been reported.⁹ This case highlights another potential pitfall associated with the current COVID-19 pandemic vaccination program, which may result in incorrect image interpretation and inadvertent disease upstaging.