FUKUSHIMA Mitsuhiro, MIYAUCHI Akira

Mitsuhiro FUKUSHIMA, Akira MIYAUCHI

Department of Surgery, Kuma hospital, Japan

キーワード :

【Background】
The incidence of thyroid cancer increased drastically in many countries, while thyroid cancer mortality remained stable. The increase was regarded due to increased detection of small papillary thyroid carcinoma because of the prevalence of imaging studies. A screening study with ultrasound and fine needle aspiration for thyroid cancer found 3.5％of Japanese adult women having small thyroid cancer. The incidence was similar to those of latent thyroid cancer in autopsy studies and more than 1000 times the prevalence of clinical thyroid cancer in Japan. These findings strongly suggested overdiagnosis and overtreatment of PTMC．In 1993，active surveillance for low-risk PTMC was initiated by Akira Miyauchi in Kuma Hospital under the hypothesis that most low-risk PTMC do not or very slowly grow and it is not too late to treat PTMC after showing progression signs such as size enlargement and novel appearance of nodal metastases. Our strategy was adopted in the newest version of ATA guidelines.
【Active Surveillance of low-risk PTMC】
In our data, only 8％and 4％of patients showed size enlargement（≥ 3 mm compared with initiation of surveillance）, and novel appearance of node metastasis, respectively after 10-year observation. Importantly, none of the patients during surveillance showed distant metastasis or died of thyroid carcinoma. Our recent study revealed that immediate surgery group had definitely higher incidences of unfavorable events, such as temporally and permanent vocal cord paralysis and hypoparathyroidism than active surveillance group. In Kuma Hospital, for patients with low-risk PTMC, we strongly recommend active surveillance as the best choice.
【Indication of fine needle aspiration cytology（FNAC）for thyroid nodules】
FNAC is a useful examination for diagnosis of thyroid nodules as well as ultrasonography. However, as FNAC is an examination with a pain, in considering of overdiagnosis and overtreatment, the indication should be chosen carefully. Japan Association of Breast and Thyroid Sonology（JABTS）published the indication of FNAC for thyroid nodules in 2008. For solid nodules, which are less than 5mm and show no ultrasonographic findings of malignancy, FNAC is not recommended. For cysts, which are less than 20mm without solid outgrowth in the cyst, FNAC is not recommended.