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.