Metachronous Adenocarcinoma of Lung in the setting of Metastatic Gastric Neuroendocrine Tumor: value of elucidating discordance on Dual Tracer PET/CT (¹⁸F-FDG and ⁶⁸Ga-DOTATATE)

Abstract

Dual tracer PET/CT examinations (¹⁸F-FDG/⁶⁸Ga-DOTATATE) have become an established practice in management of metastatic Neuroendocrine neoplasms (NENs) and demonstrates the advantages of deciphering the molecular PET characteristics of the tumor in patient management. Judicious elucidation of the findings is important, especially in scenarios of discordance with reported histopathology; this can lead to unsuspected diagnosis such as second primary malignancies (SPMs). Such diagnosis established in early disease course and mostly in an asymptomatic stage, provides patient a lead time for timely appropriate management. This concept is elaborated with a case-example of incidentally detected ¹⁸F-FDG avid metachronous adenocarcinoma lung in a patient of metastatic well-differentiated gastric NEN, wherein dual tracer PET/CT assessment had demonstrated FDG avid but non-⁶⁸Ga-DOTATATE avid lung opacity.