Metastatic Hemangiopericytoma of the Thyroid Gland / 대한갑상선학회지

Hemangiopericytoma (HPC) is a mesenchymal neoplasm constituting a minor portion of vascular tumors. Although HPCs are generally benign, some progress in a malignant course, leading to recurrence and metastasis even after radical surgery. We present a case of metastatic HPC of the thyroid gland, a very rare site of occurrence. Histological findings revealed a single, well-margined mass with high cellularity. Tumor cells were tightly packed spindle-shaped to round cells arranged around numerous thin-walled vessels. Tumor cells showed cytoplasmic immunoreactivity for CD34 and CD99. To our knowledge, this is the eleventh case reported worldwide and the first case in South Korea.