Thyroid tissue metastases from primary carcinomas of other organs represented a very small population among all thyroid surgeries. Balta et al. [13], this rate was 0.69% and Calzolari et al. [14] contributed to the literature by finding 0.15%. In all of our thyroidectomies, we found that metastatic carcinomas of other organs represented a population of 0.31%, which is consistent with the literature.

Tang et al. [7] reported an approximately sixfold difference between the incidence of thyroid metastases of lung carcinoma and renal cell carcinoma, while Nixon et al. [12] and we found the incidence to be equal in our study.

Nixon et al. [12], patients with thyroid metastases have an asymptomatic course. We did not detect any significant symptomatic findings before surgery.

Ghossein et al. [4] found a median age of 63.00 years in their population. In our study, the median age was found to be 64.00 years. Similar to this study, the female/male ratio was found to be 1 in our study.

When we searched the literature, we could not find a study on nodules with malignant cells in thyroid tissue in other organ metastasis to the thyroid gland. According to our data, the median diameter was 2.85 ± 3.75 cm. Likewise, when we evaluated the extrathyroidal invasion, lymphatic invasion and vascular invasion status of the patients included in our study population, we found extrathyroidal invasion with a frequency of 25%, lymphatic invasion with a frequency of 50% and vascular invasion with a frequency of 50%. However, there was no relevant study in the literature. We think that this limitation is due to the fact that studies are generally performed on autopsy series rather than clinically [5, 6] and the working patient group is very rare [3, 13, 14].

The overall postoperative survival of carcinoma metastases from organs secondary to thyroid tissue has been reported to be approximately 24 months [12, 15]. In our study, the median overall survival was 13 months. The limitation of the number of patients in all studies prevents a clear median value from being given.

Ljungberg et al. [16] recommend metastasectomy for renal cell carcinoma metastases except for metastatic areas treated with radiotherapy. Squamous cell carcinoma metastases, on the other hand, have poor overall survival [17]. We observed that disease-free survival after surgery was higher in the renal cell carcinoma group than in the squamous cell carcinoma group, but the time from primary diagnosis to metastasis was also longer. In our study, no patient experienced mortality during the follow-up period. Cichoń et al. [3] found no mortality in patients with isolated thyroid metastases. This was supported by our study.

Medas et al. [18] published a case report in which they evaluated isolated thyroid metastasis. In their study, they recommended total thyroidectomy if there is no metastatic condition elsewhere. They even stated that lobectomy is also an option in these patients if appropriate. Congui et al. [19] and Cichoń et al. [3] also recommended total thyroidectomy in patients with isolated thyroid metastases. We performed total thyroidectomy in all of these patients. The prognosis was good after total thyroidectomy, but we could not evaluate the feasibility of lobectomy if appropriate, because total thyroidectomy was indicated in the patients included in the study.

Although thyroid tissue is an organ rich in blood supply, it is rarely the site of metastasis [20].

This situation is surprising. Nevertheless, when malignancy is suspected in thyroid tissue in patients with a history of primary other organ carcinoma, the possibility of a metastatic focus should be considered before considering it as secondary.

In our study, no recurrence and mortality were detected in secondary thyroid malignancies after total thyroidectomy. As a result, we think that total thyroidectomy may be an adequate treatment option for secondary thyroid malignancies.