Hemangioendothelioma of the Thyroid Gland — True Endothelioma or Anaplastic Carcinoma?

After a critical histological re-examination of 26 cases of malignant hemangioendothelioma of the thyroid, and a comparison with 51 cases of anaplastic spindle and giant cell carcinoma, it becomes obvious that traumatic and shrinkage artefacts due to fixation, as well as superimposition of neoplastic and repair processes due to regressive changes — almost always seen in malignant hemangioendothelioma associated nodular goiter — may be misinterpreted as neoplastic vascular spaces (and therefore angioblastic tumour differentiation). Focal epithelial arrangements of tumour cells often observed in these malignant hemangioendotheliomas and the lack of objective light microscopic differential diagnostic criteria of anaplastic spindle and giant cell carcinoma make the high incidence of endotheliomas of the thyroid in European endemic goiter regions very questionable. Compared with anaplastic spindle and giant cell carcinoma, the incidence for (1) extrathyroid tumours that infiltrate into the trachea or the oesophagus, (2) lymph node metastases and (3) distant metastases is not statistically different in malignant hemangioendothelioma. Therefore we conclude that the tumours classified as malignant hemangioendothelioma in goitrous areas represent a special growth pattern of anaplastic spindle and giant cell carcinoma within adenomatous glands rather than a distinct tumour type.