Differentiated thyroid cancers are the most common malignant epithelial tumors of the thyroid body that arise from follicular cells exhibiting certain morphological and functional characteristics similar to that of normal thyroid tissue. They represent papillary cancers, the most common (80%) and follicular cancers [8].

The thyroid nodule is the most common manifestation of thyroid cancer. It is often asymptomatic and clinically detectable in 4 to 7% of the general population; their frequency increases with age, particularly in women [9,10]. Thyroid nodules are rarely isolated and are most often part of a GMHN. The risk of cancer is similar whether it is a solitary nodule or a GMHN. In our study, the majority of patients presented for nodular goiter, i.e. 48.7%.

Cervical lymphadenopathy is often a mode of metastatic revelation of thyroid cancer, even more rarely, it involves pulmonary or bone metastasis and confirmation of the diagnosis is essentially based on the demonstration of thyroglobulin by immunohistochemistry on the biopsy or excision of metastatic lesions [2,6].

Differentiated thyroid cancers are usually limited to the thyroid gland. Rates of distant metastases vary between 4 and 15%[1,18]. In our study these metastases were synchronous in 10% of cases and metachronous in 18% of cases. These results are close to other studies….

The location and frequency of distant metastases vary depending on the histological type. The mode of dissemination is different in the two types of cancer. Papillary cancer is known to metastasize via the lymph nodes, while follicular cancer metastasizes hematogenously, which explains its distant spread compared to papillary thyroid cancer [9,10].

In addition to the lymph nodes, the most common sites of metastases are the lungs and bone, however involvement of other organs is possible of which it represents < 5% [6].

In our patients, it was rather lymph node metastases which were the most frequent with a percentage of 77%, while bone and lung metastases represented only 23% and 20% respectively, the other sites were 7.7%.

Advanced age, high TNM stage, capsular breakage and multifocality are poor prognostic factors identified in our study. These results are consistent with the work of other studies [1,4], which indicate that age greater than 55 years, aggressive histopathological characteristics and local tumor extension or distant metastases are indicators of poor prognosis.

Total thyroidectomy from the outset is the standard treatment of choice for metastatic CDT. In our series, all patients had undergone total thyroidectomy except one due to tumor adhesion.

Total thyroidectomy with lymph node dissection is recommended for CDT with locoregional extension, according to the guidelines of the American Thyroid Association (ATA)[1,4,18] but the indications and extent of cervical lymph node dissection in thyroid cancer are still controversial, with the possibility of very different attitudes, particularly with regard to prophylactic cures. It is recommended to carry out a dissection if suspicious cervical lymphadenopathy is identified pre- or intra-operatively in order to reduce the risk of recurrence in low-risk patients and to improve survival in high-risk patients. [12].

Iratherapy remains the essential element in the treatment of distant metastases of the CDT after total thyroidectomy [13,14,15]. Its objective is:

- Treat possible macro or microscopic post-operative tumor foci.

- Destroy normal thyroid tissue to improve the sensitivity of subsequent monitoring (thyroglobulin dosage);

- Carrying out the extension assessment using whole body scintigraphy carried out 3 to 7 days after the iodine dose.

This treatment is administered in the form of an iodine 131 capsule at a dose of 3.7 GBq/course after stimulation of TSH. The latter is achieved by weaning the hormonal treatment for 3-4 weeks or after two injections of exogenous human recombinant TSH (thyrotropin alfa, Thyrogen) 24 hours apart. The effectiveness of this treatment depends on the ability of the tumor tissue to fix radioactive iodine and the volume of the tumor tissue. The iodine 131 courses are repeated every 6 to 12 months, then more spaced apart, as long as significant fixation persists and there is a morphological and/or biological and/or scintigraphic response without exceeding a dose of 22 GBq. Pulmonary micrometastases represent the most favorable situation for observing a cure thanks to iodine 131. Unlike pulmonary macrometastases and bone metastatic locations where we note an analgesic effect and stabilization of the lesions.

When the metastatic lesions are immediately non-fixing or iodo-fixing, progressing despite treatment with IRA therapy and persistent after treatment with an iodine 131 dose of 22GBq, they are considered refractory [6,9]. Although radioactive iodine ablation (RAI) therapy is the first-line treatment for metastatic disease, one third of patients do not absorb 131I or become refractory to RAI [3,6,16]. In the latter group, alternative treatments such as external beam radiotherapy, multikinase inhibitors and targeted therapies for tumors with specific molecular alterations have mainly led to an increase in the time to progression [7–10]. Given that almost a third of patients with metastatic disease may remain stable for up to 10 years or more [3, 11], active surveillance is a rational approach to patient care while limiting surgical or pharmacological interventions to those with progressive disease or mass effect symptoms.

Patient monitoring is done through clinical examination, serum thyroglobulin measurement, cervical ultrasound and iodine 131 scintigraphy. The 10-year survival rate in the presence of metastases varies from 25 to 40% [7]. It is more favorable in papillary, well-differentiated forms whose chest x-ray image is normal or miliary type, occurring before the age of 45 and respond to iodine 131.

In our series, 97% of patients received iratherapy, reflecting this standard approach.