[Is the new WHO's histological typing clinically useful for the diagnosis of follicular cancer of the thyroid?].

We tried to re-diagnose our 57 cases of thyroid follicular cancer between 1965 and 1988 in accordance with Histological Typing of Thyroid Tumours published by WHO in 1988. 1) The incidence of follicular cancer in differentiated cancers was decreased from 17.9% to 8.3% (26 cases). The number of widely invasive type and minimally invasive type was 13 cases equally. 2) Twenty four cases were diagnosed as papillary cancer. The reason was that 20 cases had a small focus of papillary structure, and other 4 cases had features of follicular variant type of papillary cancer. These 24 cases had good prognosis as our 262 cases of papillary cancer, in contrast to 26 cases of follicular cancer having worse prognosis. 3) The incidence of distant metastasis in follicular carcinoma was increased from 28.1% to 42.3%; 23.9% in minimally invasive type and 61.5% in widely invasive type, respectively. New WHO classification is acceptable according to this clinical study of our cases. We would have to treat more aggressively the patient diagnosed follicular cancer by WHO classification because of high incidence of distant metastasis.