Thyroid spindle-cell tumor with mucous cysts. An intrathyroid thymoma?

An apparently new tumor entity of the thyroid is reported. The tumor was histologically characterized by good demarcation, lobular pattern, keratin-positive spindle cells, glandular elements, stromal hyalinization, and calcifications. These findings are suggestive of a tumor related to spindle-cell thymoma and apparently closely related to the recently described entity, ectopic hamartomatous thymoma. The patient, a 23-year-old man is alive and well 10 years after diagnosis. Two histologically similar cases have earlier been reported in the English literature under the heading "malignant teratoma."