Grade 3 metastatic neuroendocrine neoplasms of two unusual primary sites with contrasting differentiation characteristics: Dual tracer positron emission tomography and computed tomography imaging (F-fluorodeoxyglucose and Ga-DOTATATE) correlates and their treatment implications.

The correlates of dual tracer positron emission tomography and computed tomography (PET-CT) (F-fluorodeoxyglucose [F-FDG] and Ga-DOTATATE) in patients of Grade 3 neuroendocrine neoplasms (NENs) are presented. The first, a patient of gall bladder NEN, operated, with histopathology suggestive of high-grade well-differentiated neuroendocrine tumors with MiB-1 labeling index of 35%, showed uptake with both F-FDG and Ga-DOTATATE, including an uptake equivalent to Krenning score of 3-4 on Ga-DOTATATE PET-CT; in the second, a patient of esophageal NEN, Grade 3 with poor differentiation features, with MiB-1 labeling index of 70%, thereby qualifying for Grade 3 neuroendocrine carcinoma, the FDG uptake was high with minimal uptake on Ga-DOTATATE PET-CT. The illustrations reiterate the impression that relative uptake of Ga-DOTATATE/FDG in the NEN lesions forms a valuable parameter for assessing the dynamic tumor biology in continuum and thus personalizing the treatment strategies.