Carcinoma of the thyroid gland.

Thyroid cancer is not a common cancer and consists of a variety of tumors with different biological characteristics. Diagnosis and therapeutic approaches differ considerably, depending on which subgroup the tumor belongs to. Differentiated carcinomas, which constitute the bulk of thyroid carcinoma, often retain the features of the thyroid gland, which can be taken advantage of in their management. The prognosis of these patients is usually excellent. Undifferentiated carcinoma, in contrast, is an aggressive tumor and usually is fatal within a year from the diagnosis. Therefore, an aggressive therapeutic approach is required. Transformation of differentiated carcinoma to undifferentiated carcinoma does occur, although infrequently. The importance of proper management of patients with differentiated carcinoma is obvious. Medullary carcinoma, which originates from the parafollicular cells, has various interesting biological characteristics and is a medium-grade malignancy.