Incidental Detection of a Melanoma by 18F-Fluorocholine PET/CT Performed for Evaluation of Primary Hyperparathyroidism

Nuclear medicine imaging modalities to detect incidentalomas and their impact on patient management: a systematic review

PURPOSE

This systematic review aims to investigate the role of nuclear imaging techniques in detecting incidentalomas and their impact on patient management.

METHODS

Following PRISMA guidelines, a comprehensive literature search was conducted from February to May 2022. Studies in English involving patients undergoing nuclear medicine studies with incidental tumor findings were included. Data on imaging modalities, incidentaloma characteristics, management changes, and follow-up were extracted and analyzed.

RESULTS

Ninety-two studies involving 64.884 patients were included. Incidentalomas were detected in 611 cases (0.9%), with thyroid being the most common site. PET/CT with FDG and choline tracers showed the highest incidentaloma detection rates. Detection of incidentalomas led to a change in therapeutic strategy in 59% of cases. Various radiotracers demonstrated high sensitivity for incidentaloma detection, particularly in neuroendocrine tumors and prostate cancer.

CONCLUSION

Nuclear imaging techniques play a crucial role in detecting incidentalomas, leading to significant changes in patient management. The high sensitivity of these modalities highlights their potential in routine oncology follow-up protocols. Future directions may include enhancing spatial resolution and promoting theranostic approaches for improved patient care.

Incidental Findings on 18F-Fluorocholine PET/CT for Parathyroid Imaging

Introduction   ¹⁸ F-choline positron emission tomography/computed tomography (PET/CT) is an upcoming imaging technique for the localization of hyperfunctioning parathyroid glands. However, ¹⁸ F-choline is a nonspecific tracer that also accumulates in malignancies, inflammatory lesions, and several other benign abnormalities. The aim of this study was to determine the occurrence and relevance of incidental findings on ¹⁸ F-choline PET/CT for parathyroid localization.

Materials and Methods   ¹⁸ F-choline PET/CTs performed in our center for parathyroid localization from 2015 to 2019 were reviewed. Abnormal uptake of ¹⁸ F-choline, with or without anatomical substrate on the co-registered low-dose CT and also incidental findings on CT without increased ¹⁸ F-choline uptake were recorded. Each finding was correlated with follow-up data from the electronic medical records.

Results  A total of 388 ¹⁸ F-choline PET/CTs were reviewed, with 247 incidental findings detected in 226 patients (58%): 82 ¹⁸ F-choline positive findings with corresponding pathology on CT, 16 without CT substrate, and 149 ¹⁸ F-choline negative abnormalities on CT. Malignant lesions were detected in 10/388 patients (2.6%). Of all 98 detected ¹⁸ F-choline positive lesions, 15 were malignant (15.3%), concerning 4 metastases and 11 primary malignancies: breast carcinoma ( n  = 7), lung carcinoma ( n  = 2), thyroid carcinoma ( n  = 1), and skin melanoma ( n  = 1).

Conclusion  Clinically relevant incidental findings were observed in a substantial number of patients. In 15.3% of the incidental ¹⁸ F-choline positive findings, the lesions were malignant. These data contribute to better knowledge of ¹⁸ F-choline distribution, enhance interpretation of ¹⁸ F-choline PET/CT, and guide follow-up of incidental findings. Attention should especially be paid to breast lesions in this particular patient group with hyperparathyroidism in which women are typically over-represented.

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

A 47-year-old woman with a history of surgically treated abdominal paraganglioma and left thigh melanoma underwent an F-FDOPA PET/CT for suspected locoregional recurrence of paraganglioma. F-FDOPA PET/CT disconfirmed this recurrence but revealed 2 FDOPA-avid left inguinal lymph nodes, confirmed on a subsequent F-FDG PET/CT. Excision and pathology characterized these lymph nodes as melanoma metastases. F-FDOPA PET/CT is a widely used and valuable tool in the assessment of paraganglioma, both for staging and recurrence detection. Uptake of FDOPA has only rarely been documented in metastatic melanoma that could be a pitfall for detecting neuroendocrine tumors.

Choline PET/CT in parathyroid imaging: a systematic review

One of the most promising imaging techniques in primary hyperparathyroidism is PET/CT with choline-based tracers. To investigate the current evidence of these tracers in localizing parathyroid adenoma, a systematic review was performed. A comprehensive literature search was carried out and eligible studies were analyzed. Data were extracted, the level of evidence was scored, and performance data were pooled to calculate the weighted detection rate. Eleven articles were included in this study. The pooled detection rate was 97 and 94% on per patient-based and per lesion-based analysis, respectively. There was considerable heterogeneity between studies and the level of evidence was determined to be 3a-, following Oxford criteria. Choline PET/CT has shown favorable results in detection of hyperfunctioning parathyroid tissue and may replace conventional technetium-99m-sestamibi scintigraphy in preoperative planning of parathyroid surgery. However, the quality of current evidence is moderate, and additional high-quality studies are needed to confirm these numbers.