A total of 96 patients underwent completion thyroidectomy for PTC and 22 patients for FTC. The mean age at the time of surgery was 41.7 years (Age range from 79 to 13 years,). There were 90 (76%) women and 28 (24%) men.

Right completion thyroidectomy was essential in 23 patients (19%) and left completion thyroidectomy in 27 patients (23%), respectively. In all, 68 patients underwent completion thyroidectomy on both sides (58%).

Lymph node dissection was done in 99 patients (84%) (Table 1): 68 patients (58%) underwent central lymph node dissection on both sides and 31 patients (26%) underwent lateral lymphadenectomy (ipsilateral, n = 21; contralateral, n = 10). All patients had to be reoperated on the side of the primary operation for resection of remaining thyroid tissue and/or lymph node dissection. The mean number of dissected lymph nodes was 13 (range 5 - 33).

Adhesions were documented in 71 patients (60%). In 53 cases these adhesions were described as severe (45%). There was significant difference between the three groups (groups A-C) where sever adhesion more in group A. Auto transplantation of parathyroid glands had to be performed in 7 patients due to accidental removal or intraoperative affection of the blood supply.

In the final histology, 30 patients exhibited multicenteric thyroid carcinoma

CT: completion thyroidectomy, bCT: bilateral completion thyroidectomy, pLND: prophylactic lymph node (ln) dissection (ln-), tLND: therapeutic lymph node dissection (ln?), **p value < 0.005.

(25.5%). PTC (27/96) was diagnosed in 23 of these patients and four patients had PTC with an FTC variant, and three patients had invasive FTC. In 62 cases the completion thyroidectomy specimen comprised residual tumor (52.5%). Twenty eight patients showed contralateral secondary cancer (24%). No additional tumor cells were detected histologically after completion thyroidectomy in 56 patients (47.5%). Lymph node positive in 56 patients (47.5%). PTC was diagnosed in 53 of these patients.

Particular postoperative complications after completion thyroidectomy were hypocalcemia and vocal cord paresis (VCP). Twenty five patients developed transient postoperative hypocalcemia (21%). five patients required long-term IV and oral calcium substitution for persistent hypoparathyroidism (4.2%). The rates of persistent hypocalcemia were significantly higher in groups A, and B as compared to those of groups C (p < 0.005) (Table 1). Transient VCP was detected in twelve patients (10%) and persistent VCP in three patients (2.5%). Recurrent laryngeal nerve (RLN) palsy happened more frequently in groups A and B (p < 0.005) (Table 1). There was persistant bilateral VCP in one patient, in whom transient tracheotomy had to be performed. Other morbidity include pleural injury in one patient in group A, Horner’s syndromes in 2 patients one in group A and the other in group C.

Multiple surgeries were performed in 9 patients where 2 patients develop transient hypocalcemia.

Postoperative radioactive iodine treatment was achieved in 112 patients (95%). The mean number of therapy courses was two (range 1 - 7). At the time of follow-up 107 patients were thriving and disease-free (90.5%). Twelve patients (10.3%) were treated for local recurrence (n = 9) or distant metastasis (n = 3). Two patients developed bone metastasis from FTC and one patient developed lung metastasis from PTC with follicular element. The PTC patient additionally showed loco-regional metastases.

Nine patients died during the follow-up. Two of these seven patients died disease progression and seven patients for other causes. Because of the low number of events (two), the cancer related overall survival could not be considered. Nevertheless, there was no important difference among the three groups regarding disease-free survival during the follow-up.

The indication for completion thyroidectomy in patients with incidentally established differentiated thyroid tumor after primary thyroid operation should consider patient-related, tumor-related, and treatment-related criteria [6] .

In the current study 96 of 118 patients had PTC. This object is frequently concomitant with local lymph node metastasis. Furthermore, multicenter tumor localization is common [10] [11] [12] .

Auguste and Attie [13] reported multifocal PTC in 33 of 80 patients (41.2%) and contralateral PTC in 30 of 80 patients (37.5%) after completion thyroidectomy. In current series, the general rate of multifocal PTC was 28% (27/96). Multicenteric tumor localization has been presented to be accompanying with a higher risk of lymph node metastasis and local lymph node recurrence [10] . Thus, secondary total thyroidectomy and local lymph node dissection should be completed in all cases except patients with unifocal papillary microcarcinoma (> 1 cm) without metastasis and/or infiltration of the thyroid capsule [14] [15] .

In the current study, 22 patients (19%) were operated on for FTC. three of these patients had multifocal FTC (13.5%). It is well reported that hematogenous distant metastases can be found in 10% of patients with minimally invasive FTC and 50% of patients with widely invasive FTC. Thus, complete thyroidectomy is advised in all patients with FTC. The need of completion thyroidectomy after R0 resection during primary subtotal thyroidectomy in minimally invasive FTC without vessel infiltration or metastasis remains controversial [5] [14] .

Still, suspicious nodules could be frequently detected after incomplete thyroidectomy by high-resolution ultrasonography [16] .

Lymph node dissection should be performed in all patients with node-positive FTC [14] [15] .

In 62 patients remaining tumor was detected histologically in the secondary resected sampling in our series (52.5%), supporting the indication for completion thyroidectomy in most patients with differentiated thyroid carcinomas.

It is away from question that secondary cervical operation, if made on the ipsilateral side, increases the operational hazard after subtotal thyroidectomy. In the current study, the rate of persistent VCP and persistent hypocalcemia was 0% in groups C (< 6 months after primary surgery) (Table 1). There was a major increase in transient and persistent postoperative VCP groups A and B ranging from 3.1% to 9.3% and 3.3% to 6.7% respectively (p < 0.005). In the literature, the rate of transient VCP is about 20% and the rate of permanent VCP ranges between 1.5% and 5.3% [16] [17] [18] . Reports of persistent hypocalcemia rates range between 1% and 4% in our study rate of persistent hypocalcemia range from 4.7% to 6.6% for group A and B respectively [13] [16] [19] .

The impact of the timing of secondary operation on postoperative morbidity is still debatable. In some reported studies, the frequency of postoperative complications was independent of the period between the primary and completion operations [17] [20] [21] [22] .

In two of these studies the rates of persistent VCP were 1.6% and 2.7%, respectively. Persistent hypocalcemia occurred in 4.8% and 0.9% of patients after completion thyroidectomy [17] [21] .

In contrast, Walgenbach and Junginger [16] described decreased postoperative morbidity in patients operated on within the first week or 3 months after primary operation. The rates of transient VCP were 5.2% in patients with completion thyroidectomy within 1 week or after 3 months and 20.5% with the operation between 8 days and 3 months. The rate of persistent VCP was also expressively higher in patients operated on between 8 days and 3 months after primary surgery. Tan et al. [23] reported rates of transient hypocalcemia in 3.1% for <10 days or >3 months and 10.8% for between 10 and 90 days after primary operation, respectively. There was no persistent hypocalcemia in this series. The rise in morbidity between 1, 3, and 6 months after incomplete thyroidectomy described in our study may be due to strong postoperative fibrosis and adhesions, which often decrease or entirely disappear after that period. Interestingly, there was no significant difference regarding the overall rate of patients with adhesions among the 3 groups. However, due to retrospective data analysis from surgical reports without using defined adhesion scores, the informative value regarding intraoperative adhesions is strongly predisposed by the surgeon’s subjective estimation and is therefore imperfect.

The early histopathologic diagnosis of thyroid tumor is essential to permit early completion surgery. Thus, intraoperative frozen section assessment is recommended, particularly in patients with signs of malignancy. If frozen section is not accessible, a proper histopathologic diagnosis should be offered within 48 - 72 h, following the German Association of Endocrine Surgeons practice guidelines [24] . In patients with follicular neoplasm, an intraoperative diagnosis of malignancy may be challenging because follicular lesion often necessitate detailed analysis to detect capsule infiltration or vascular invasion [25] . Also in these cases, conclusive histopathologic diagnosis should be available within 72 h.

For this reason our study did not include patients where secondary operation done during 1^st week of primary surgery as final diagnosis usually established after one week.

In addition to perioperative morbidity, the oncologic outcome of patients with differentiated thyroid tumor after incomplete thyroidectomy must be taken into account regarding the indications and timing of completion surgery. Considering the small number of patients and the limited follow-up time, there was no important difference between the 3 groups regarding tumor recurrence or disease progression in our series.

In agreement with this trend, Walgenbach and Junginger [16] , in a larger study, reported no effect of the timing of the completion thyroidectomy on survival or recurrence. Scheumann et al. [26] showed that completion thyroidectomy within 6 months of the primary surgery significantly reduced the risk of recurrence and lymph node and hematogenous spread. It also improves survival in contrast to patients in whom the second operation was delayed for longer than 6 months. Furthermore, there is no evidence of metastasis arising from existing metastases of differentiated thyroid tumor. Nevertheless, an increased risk of disease progression after R1 or R2 resection has to be assumed. In our belief, at least 3 to 6 month interval between primary and secondary surgery can be justified.