Discussion and Conclusions
TAS is a rare and aggressive mesenchymal tumor, which has been the subject of controversy, especially when it comes to it being differentiated from anaplastic thyroid carcinoma. For years it was considered a vascular mutation of anaplastic carcinoma and not a true sarcoma. The first recorded case of angiosarcoma was in 1986, when immunohistological techniques confirmed the endothelial origin of the tumor [10]. Primary angiosarcoma was only recognized as a distinct entity in the WHO classification in 2013 [11].
Histologically, TAS is characterized by areas of extensive necrosis and bleeding with the presence of endothelial cells. The neoplastic cells are large with a high mitotic index and tumor necrosis prevails. In addition to cytokeratin, neoplastic cells also express endothelial markers, which allow differentiation from anaplastic carcinoma. In a bibliographic report of 23 patients, positive immunohistochemical staining for endothelial markers or cytokeratin was observed in all cases [12]. Specifically, CD31 was positive in all 19 patients tested, while CD34 was positive in 7 of 16 cases (44%). Factor VIII was positive in 20 of 23 patients (87%) and cytokeratin in 22 of 23 (96%). Therefore, cytokeratin, which is also expressed in anaplastic carcinomas, does not help in the differential diagnosis from anaplastic carcinoma, as opposed to CD31 and factor VIII, which in combination with tumor morphology, essentially determine the endothelial origin of the tumor [12]. Another essential characteristic of TAS is the negative expression of thyroglobulin, which differentiates angiosarcoma from anaplastic carcinoma, in which thyroglobulin is mildly expressed [13], [14].
TAS is a particularly aggressive tumor with poor prognosis, as confirmed from the latest literature review that cites all the known 59 cases, in 89.3% of which death occurred within 9 months [8]. Death occurs due to rapid metastases to lymph nodes, lungs, bones and soft molecules [3]. Infiltration of the trachea and esophagus are also common. Capsule infiltration and distant metastases represent the most negative prognostic factors, whereas a better prognosis is expected when TAS is limited to the thyroid gland and is combined with aggressive treatment [15], [16].
Due to the rarity and the small number of TAS cases, no gold standard of treatment has been established. Undelayed radical surgery along with complementary radiation seems to improve prognosis and overall survival and is, therefore, recommended as the best approach based on the data so far [17]. Sarcomas should be approached by many specialties and if it is possible, they should be treated at a referral centre [18]. Chemotherapy may also have a local and systemic effect on disease control [19], nonetheless, more studies are needed to determine the role of chemotherapy [20]. Radioactive iodine has no place in the treatment of vascular sarcoma, since the cells are not of thyroid origin and new drugs, such as anti-VEGF agents [21] and paclitaxel [22], have been tested without satisfactory results.
In conclusion, the present case is the 60th to be reported in the literature. Raising awareness to clinicians about this tumor is important so that early diagnosis and treatment increase the chances of survival. In addition, recording new cases of this rare neoplasm that provide additional data on treatment, the course of the disease and the final outcome, may help identify the best treatment approach in order to improve prognosis and overall survival.