[Follicular carcinoma with sarcomatoid dedifferentiation or thyroid gland carcinosarcoma?].

Thyroid carcinoma may at times display unusual clinical and anatomo-pathologic behaviour. The case of a female patient associating goiter of long standing with a fulminating terminal course is presented. Since the patient was never treated, the evolution of her condition is thought to reflect the natural biologic behaviour of the disease process. Pathologic examination revealed the co-existence of both follicular and anaplastic carcinoma within the primary lesion. Moreover, metastases were either entirely follicular or poorly differentiated in structure, and occasionally even of striking sarcomatoid appearance. The possibility of carcinosarcoma was entertained but dismissed in view of the recent literature. Rather, the hypothesis of tumour dedifferentiation offers a more satisfactory explanation for the clinical course and pathologic findings.