Prevalence and clinical significance in our setting of incidental uptake in the thyroid gland found on 18F-fluordeoxyglucose positron emission tomography-computed tomography (PET-CT).

INTRODUCTION: The expanding use of 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) has resulted in an increased frequency of incidentally discovered areas of FDG uptake within the thyroid gland. In these incidentalomas, high malignancy rates are reported. The study aimed, on the one hand, to determine the prevalence in our setting of thyroid incidentalomas in patients with no previous history of thyroid cancer undergoing an FDG PET-CT as well as the risk of malignancy and, on the other hand, to evaluate the usefulness of the maximum standard uptake value (SUVmax) for detecting thyroid cancer. MATERIAL AND METHODS: The FDG PET-CT scans performed at our hospital between June 2013 and December 2020 were retrospectively reviewed. In those incidentalomas with sufficient additional investigation, a diagnosis of benign or malignant was established based on the complementary tests. RESULTS: From the 21,594 PET-CT scans performed, 398 (1.8%) patients had an incidental FDG uptake, either focal (n=324) or diffuse (n=74). Among incidentalomas with further investigation, the rate of malignancy was higher in patients with focal FDG uptake than in those with diffuse uptake (26.5% versus 4%, respectively, p<0.05). The SUVmax value was significantly lower in benign focal lesions (5.7 [range: 2.3-66] than in malignant ones 10.6 [range: 3.1-51.2]; p<0.05). Nearly a quarter of malignant diagnoses (23.3%) were related to potentially aggressive tumours. CONCLUSION: The high rate of malignant tumours found among PET-CT incidentalomas and the high proportion of aggressive tumours demonstrate the need for a standardised approach in the investigation of incidental focal FDG uptake in the thyroid gland.

Accuracy of sentinel node mapping in patients with biopsy-proven metastatic axillary lymph nodes and upfront surgery: preliminary results of the Multimodal Targeted Axillary Surgery (MUTAS) trial.

Background: Some studies suggested that the patients included in the Z0011 trial may represent patients with ultrasound-negative axillary nodes and axillary invasion diagnosed by sentinel node (SN) biopsy. Nevertheless, the National Comprehensive Cancer Network (NCCN) guidelines recommend SN mapping if 1 or 2 suspicious lymph nodes are identified on axillary ultrasound (AU). The aim of this preliminary phase of the Multimodal Targeted Axillary Surgery (MUTAS) trial was to establish the accuracy of SN mapping in patients with axillary involvement undergoing upfront surgery. Methods: Between September 2019 and March 2022, we recruited patients with biopsy-proven metastatic axillary nodes and upfront surgery from a single center. We performed SN mapping in these patients before the surgical intervention, which included axillary lymph node dissection. The biopsy-proven metastatic node, SNs and the remaining axillary nodes were excised separately. SN status was considered representative of the status of the remaining axillary nodes. We calculated the sensitivity, specificity, negative predictive value and positive predictive value of the SN, overall and in patients with palpable nodes, in those with non-palpable nodes and an AU leading to diagnosis of axillary involvement, in those with 1 or 2 suspicious nodes on AU, and in patients with a single suspicious node on AU. We evaluated clinical, imaging and pathology features as predictors of the status of the remaining axillary nodes, false-negatives, and false-positives. Results: We included 25 patients in this phase. The false-negative rate of SN mapping was 28% overall, 21.42% for patients with palpable nodes, 36.36% for patients with non-palpable nodes and an AU diagnosis of axillary involvement, 28.75% for those with 1 or 2 suspicious nodes on AU, and 15.38% in patients with a single suspicious node on AU. The negative predictive value was highest in patients with a single suspicious node on AU (75%). The only significant predictive factor was that FN showed a higher Ki67 index score. Conclusions: In this study, SN mapping was not reliable in patients with biopsy-proven metastatic axillary nodes and upfront surgery for any of the subgroups studied. Further research should elucidate the best staging pathways in these patients to avoid premature de-escalation.