[Hemangiopericytoma of the thyroid gland].

Hemangiopericytoma is an uncommon tumour of the thyroid gland. We report the fourth case of thyroid hemangiopericytoma in a 77 year-old woman who presented a goiter known for 23 years. The tumour, 11.5 X 7 X 7 cm in diameter, was located in the left lobe. Its histological features were those of a benign hemangiopericytoma as in two cases previously reported. Light microscopy discovered capillaries surrounded by sheets of plump cells and a reticulin network encircling each cell. A few tumour cells showed slight immunoreactivity with antibody against actin. There was no immunoreactivity with antibodies against desmin, vimentin and myosin intermediate filaments. Today, the electron microscopic analysis which revealed that tumour cells looked like pericytes, remains the best investigation for hemangiopericytoma diagnosis.