Incidental Metastatic Melanoma Identified on 18F-FDOPA PET/CT With Confirmation by Histology

Colorectal Adenocarcinoma Mimicking Neuroendocrine Neoplasia on 18 F-FDOPA PET/CT

ABSTRACT

We present a case of a 48-year-old woman who had previously undergone surgical resection for bladder paraganglioma. An 18 F-FDOPA PET/CT scan performed for suspected colorectal paraganglioma showed intense colorectal uptake associated with adenopathy. Histological examination did not support the presence of a neuroendocrine tumor but instead confirmed the presence of moderately differentiated colorectal adenocarcinoma. Colorectal adenocarcinoma belongs to the list of nonneuroendocrine false-positive tumors that can be detected using 18 F-FDOPA. Therefore, a morphological analysis is important. Thus, 18 F-FDOPA may be a marker for the aggressiveness of colorectal adenocarcinoma.

Molecular imaging of endocrine neoplasms with emphasis on 18F-DOPA PET: a practical approach for well-tailored imaging protocols

6-[18F]-L-fluoro-L-3, 4-dihydroxyphenylalanine (¹⁸F-DOPA) PET/CT can be a useful tool for the detection of different neuroendocrine tumors (NETs). The main determinants of ¹⁸F-DOPA uptake and retention by NETs are related to expression of LAT1/LAT2 transporters, expression and activity of AADC and biochemical phenotype, all being intimately inter-connected to their embryological origin. In order to improve sensitivity of ¹⁸F-DOPA PET, it is of main importance to perform indivisualized imaging protocols across primaries. This review provides a practical approach for performing well-tailored imaging protocols and describes the clinical value of the recommended radiopharmaceuticals.

Hepatic Cavernous Hemangioma Mimicking Metastasis of Midgut Neuroendocrine Neoplasia on 18F-Fluorodihydroxyphenylalanine PET/CT

ABSTRACT

A 61-year-old man after resection of well-differentiated midgut neuroendocrine neoplasia (NEN) was referred to 18F-fluorodihydroxyphenylalanine PET/CT for localization of recurrent midgut NEN in the context of clinical symptoms and mild elevation of serum CgA (chromogranin A) levels. Isolated hepatic focus of increased 18F-Fluorodihydroxyphenylalanine uptake was detected. The biopsy of this focus, followed by radiofrequency ablation, revealed a hepatic cavernous hemangioma. Complete remission of midgut NEN was confirmed during 4-year clinical and imaging follow-up. The persistent mild elevation of serum CgA was retrospectively attributed to treatment with proton-pump inhibitors.

Variants and Pitfalls of PET/CT in Neuroendocrine Tumors

Management of patients with neuroendocrine neoplasms (NEN) is complex and warrants referral of these patients to high volume centers with appropriate expertise to ensure favorable outcomes. PET/CT becomes increasingly important in every step of their management and outcome. The choice of radiopharmaceutical heavily depends on tumor origin, which is intimately interconnected to embryology, grade and clinical presentation (eg, diagnostic vs theranostic settings). The aim of this review is to describe the role of SSTR, ¹⁸F-FDOPA, and ¹⁸F-FDG-PET imaging in the evaluation of NEN patients. There is emphasis on the main variants, caveats, and pitfalls that can be observed within these modalities. Nuclear physicians must be equipped with the skills to handle potential variants, caveats, and pitfalls that are commonly encountered in NEN imaging, and they should understand the expected imaging features that are encountered across various types of NENs.