The recent sharp increase in thyroid cancer incidence is mainly due to increased detection of small papillary thyroid microcarcinoma (PTMC). Due to the indolent nature of the disease, active surveillance (AS) of low-risk PTMCs is suggested as an alternative to immediate surgery to reduce morbidity from surgery. For appropriately selected PTMC patients, AS can be a good management option and surgical intervention can be safely delayed until progression occurs. Many considerations must be taken into account at the time of initiation of AS, including radiological tumor characteristics and clinical characteristics of the patient. A specialized medical team should be assembled to monitor patients during AS with an appropriate follow-up protocol. The fact that some patients require surgery for disease progression after long-term follow-up is a major drawback of the current AS protocol. Evaluation of tumor kinetics by three-dimensional tumor volume measurement during the initial 2–3 years of AS may be helpful for discrimination of PTMCs that need early surgical intervention. In this review, we will discuss the clinical outcomes of surgical intervention and AS, considerations during AS, and unresolved questions about AS.

Introduction: Small-volume hydrodissection liquid dissipates rapidly and confers only short-term protection during radiofrequency ablation (RFA) of benign thyroid nodules. The aim of this study was to establish a safe method for continuous, large-volume hydrodissection. Methods: A long needle was inserted and positioned outside the thyroid capsule; 5% glucose was injected to maintain a 3- to 5-mm continuous safety buffer. From October 2015 to July 2020, 166 patients underwent hydrodissection with different volumes, and ablation efficacy and complications associated with different liquid volumes (≤40 mL vs. >40 mL) were compared at 1-month postprocedure. Moreover, 20 mL liquid (equivalent to 250 mL in the human body) was injected around the thyroid of a rhesus monkey, after which CT scans were used to visualize the liquid’s fate and verify its safety. Results: The 51 patients with 10–40 mL injections and 116 patients with larger injections (45–450 mL) showed similar complete ablation rates (88.46% vs. 90.44%, p = 0.582), comparable 6-month VRR (82.79% vs. 76.62%, p = 0.079), and complication incidences, although the latter group had larger nodules (9.11 mL vs. 13.79 mL, p = 0.003), more energy delivered (3.44 kcal vs. 6.04 kcal, p < 0.001), and longer operation times (51.37 min vs. 69.2 min, p < 0.001). In the animal experiment, the 20 mL of liquid diffused quickly (within 10 min) from the vicinity of the thyroid to the mediastinum and retropharyngeal space. It was observed in the kidneys at 10 min and disappeared from the neck and chest space by 24 h. Conclusions: Continuous, large-volume hydrodissection can protect the delicate structures around the thyroid throughout the RFA procedure and might be beneficial in large thyroid nodule ablation.

Background: It infrequently occurs that cytologic diagnosis of papillary thyroid carcinoma (PTC) cannot be confirmed by histology after surgery. This phenomenon may be a false-positive cytology or a true disappearing tumor. Objectives: We evaluated patients who had consistent findings of PTC at fine needle aspiration cytology (FNAC) and no evidence of PTC in surgical specimens. Methods: Positive cytology findings and a negative histological diagnosis of PTC in the thyroid was defined as thyroid nodules with FNAC findings of PTC prior to surgery and no evidence of malignancy on histological examination of surgically removed thyroids. We retrospectively reviewed patients who underwent fine needle aspiration (FNA) and thyroidectomy in Asan Medical Center from 2004 to 2012. Results: Six patients were found who fit the definition of positive cytology findings and a negative histological diagnosis of PTC in the thyroid. The FNAC diagnosis of 6 patients was ‘malignancy' suggesting PTC according to the Bethesda system. All patients underwent thyroidectomy with central neck dissection. Three patients had reactive changes after FNA due to needle passage. Among these 3 patients, 2 had pathologically confirmed metastatic PTC in dissected lymph nodes. These 2 patients could be defined as true disappearing PTC in the thyroid after FNA. The remaining 3 patients had neither histologic alterations nor evidence of PTC in the thyroid and lymph nodes specimens. Conclusions: Both disappearing PTC and a false-positive result of FNAC should be considered in patients with positive cytology findings and a negative histological diagnosis of PTC in the thyroid.