Angiosarcoma of the thyroid is an uncommon condition whose aetiology is uncertain. A large number of cases (representing 5% of thyroid malignancies) were reported in Switzerland in the mid-20th century. Iodine deficiency is thought to be the predisposing factor but other factors must be involved. Most patients are over 65 years in age and female.
Symptoms of angiosarcoma are similar to other thyroid malignancies with local symptoms and a painless enlarging mass. Distant metastases are common and life expectancy is < 6 months regardless of treatment.
Macroscopically the tumour contains large areas of necrosis and haemorrhage. It may have a cystic, solid or mixed appearance. A capsule may be present but tumour cells are always found beyond this structure.
Microscopically there is a high mitotic index, and channels lined by endothelial cells are commonly seen. Papillary fronds of tumour are also visible in most cases. Immunohistochemistry shows positive staining for Factor VIII, CD31 and CD34.
Other mesenchymal malignancies of the thyroid are very rare.