More Than 50% of the Patients With Clinically Unifocal T1b/Small T2 Node Negative Papillary Thyroid Carcinoma Scheduled for Thyroid Lobectomy May Require Completion Thyroidectomy if the Nodal Status is Evaluated

In absence of nodal metastases or aggressive features, thyroid lobectomy (TL) should be preferred over total thyroidectomy (TT) for small unifocal, papillary thyroid carcinoma(PTC). However, occult, despite non-microscopic (\>2 mm), nodal metastases may be present inclinically node-negative (cN0) PTC.

Among 4216 thyroidectomies for malignancy (2014-2023), 110 (2.6%) TL plus ipsilateral central neck dissections (I-CND) were scheduled for unifocal cT1b/small cT2 (\<3 cm) cN0 PTCs.

Nodes frozen section examination (FSE) was performed: when positive, completion thyroidectomy (CT) was accomplished during the same procedure. In presence of aggressive pathologic features, CT was suggested within 6 months from index operation.

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer. Although its incidence has increased in recent decades, the prognosis is excellent due to the indolent nature of disease. Despite that, recurrence rate of PTC remains common. Nowadays, the correct extent of thyroidectomy remains controversial. However, several studies demonstrated no significant differences in terms of disease-free survival (DFS) and loco-regional recurrence (LRR) in differentiated thyroid carcinoma (DTC) \> 1cm after thyroid lobectomy (TL) vs thyroid lobectomy (TT). In absence of preoperative high-risk features (HRFs), the most recent NCCN and ATA guidelines consider unifocal 1-4 cm PTC eligible for TL. However, many of HRFs are highlighted only after histological examination: positive lymph nodes, aggressive tumor subtype, multifocality, microscopic extrathyroidal extension (ETE), positive margin and lymphovascular invasion (LVI).

Recent retrospective series showed that up to 59% of preoperative low risk PCT were upgraded to higher risk category after histological examination. Current recommendations could potentially increase the need for reoperation, in terms of completion thyroidectomy (CT) and subsequent administration of RAI in order to reduce the risk of LRR. Among the HRFs, no preoperative clinical parameter is a predictor of nodal disease. However, occult lymph node metastases (LNMs) may be found in 31-62% of patients subjected to prophylactic CND (p-CND). The risk of complications (hypoparathyroidism and laryngeal nerve injury) is the main matter against prophylactic bilateral CND in unifocal node negative PCT. According to a recent systematic review, basing on prevalence of occult central LNM by tumor size, ipsilateral central neck dissection (I-CND) may be justified in all PTC patients. Since isolated contralateral metastases are rare, a routine use of frozen section examination (FSE) of I-CND may allow a more accurate staging with a reduction of morbidity. Although p-CND is not usually recommended in patients with clinically unifocal cT1b/T2 node negative PTC, we supposed that the evaluation of LN status through FSE of I-CND may contribute significantly to risk stratification and consequently to modulate the extension of surgical treatment.

In this retrospective study we aim to evaluate the result of this strategy to identify intraoperatively patients who may benefit from total thyroidectomy (TT) with bilateral CND (B-CND), reducing the need of second step CT and, theoretically, the risk of LRR.

Among 4176 patients who underwent thyroidectomy for malignancy between September 2014 and September 2023 at Fondazione Policlinico Universitario A. Gemelli - Rome, we identified X patients scheduled for thyroid lobectomy (TL) plus ipsilateral central neck dissection (I-CND) for clinically intrathyroidal unifocal cT1b/small cT2 node negative papillary thyroid carcinoma (PTC). Every patient was informed of the risks and benefits of TL and TT, based on available guidelines.

Inclusion criteria were: age\>18; classic papillary carcinoma and variants; clinically unifocal and intrathyroidal PTC; clinical tumor size \>1 cm and ≤3 cm; no clinical evidence of LN involvement.

Exclusion criteria were: age \< 18 years; prior head or neck irradiation; family history of thyroid carcinoma; clinical evidence of multifocality, extrathyroidal extension or LN metastases; follow-up \< 6 months.

Eligibility Criteria:
Inclusion Criteria:

* age\>18
* classic papillary carcinoma and variants
* clinically unifocal and intrathyroidal PTC
* clinical tumor size \>1 cm and ≤3 cm
* no clinical evidence of LN involvement

Exclusion Criteria:

* age \< 18
* prior head or neck irradiation
* family history of thyroid carcinoma
* clinical evidence of multifocality
* extrathyroidal extension or LN metastases
* follow-up \< 6 months.