Malignant neoplasm of thyroid
Thyroid cancer is a fairly common malignancy. Thyroid carcinomas (cancers) are a heterogeneous group of tumours that demonstrates considerable variability in behaviour, appearance and response to therapy. Although benign thyroid nodules are common, thyroid carcinoma is rare representing approximately 1% of all malignancies and 2% of all cancer deaths.
Recognized types of thyroid cancer and their frequency are are (1) papillary and mixed papillary/follicular, 75%; (2) follicular and Hurthle cell, 15% (3) medullary, 7%; and (4) anaplastic, 3%.
Thyroid carcinoma occurs with an incidence of approximately 36 to 60 cases per million population per year. In USA the incidence of thyroid cancer is 4 per 100,000 or about 0.004% per year. Incidence in Bombay is 0.4/100,000 in males and 1.0 per 100,000 in females. These tumours are rare in children and increase in frequency with increasing age. A female to male ratio of 2.5:1 is reported. The annual mortality from thyroid carcinoma in the United States is only 6 per million population. This discrepancy between incidence and mortality presumably reflects the favorable prognosis for most thyroid carcinomas.