Abstract
Background:Primary leiomyosarcomas of the thyroid are very rare and the characteristie cytological features have not yet been clearly elucidated. We report a case of primary leiomyosarcoma of the thyroid in which fine needle cytology was performed.
Case:The patient was an 86-year-old woman with an enlarging tumor in the left lobe of the thyroid. The smears aspirated from the tumor suggested undifferentiated carcinoma or sarcoma. Immunohistochemical staining revealed that the tumor cells were positive for a-smooth muscle actin and desmin, and negative for cytokeratin and EMA. Electron microscopy revealed spindle-shaped tumor cells containing bundles of filaments with focal densities. The final diagnosis was primary leiomyosarcoma of the thyroid.
Conclusion: Primary leiomyosarcoma of the thyroid is difficult to differentiate from undifferentiated carcinoma and other histological types of sarcoma. We consider that the differentiation requires immunohistochemical staining and electron microscopy.
