SUMMARY:A PTMC is defined as a thyroid papillary cancer that measures Յ10 mm in the greatest diameter. The detection rate for a PTMC has increased because of the worldwide use of highresolution sonography and US-FNAB. We report a case of a 1-mm-diameter PTMC confirmed at thyroidectomy for which the cytologic diagnosis had an important role in deciding the extent of surgery (ie, either a total thyroidectomy or a hemithyroidectomy).ABBREVIATIONS: ATA ϭ American Thyroid Association; HE ϭ hematoxylin-eosin; PTC ϭ papillary thyroid carcinoma; PTMC ϭ papillary thyroid microcarcinoma; US-FNAB ϭ sonography-guided fine-needle aspiration biopsy A US-FNAB is a widely used procedure for the cytological evaluation of thyroid nodules. However, US-FNAB of a thyroid nodule Ͻ10 mm in maximal diameter seems to be limited because of a poor clinical significance and social-medical-cost problem. We report a case of 1 mm diameter PTMC that was diagnosed on US-FNAB and this cytological diagnosis influenced the decision of thyroid surgery type.
Case ReportA 43-year-old woman who had recently complained of fatigue and neck discomfort was referred to the radiology department from the department of general surgery for sonographic evaluation of the thyroid. The patient showed normal values on a thyroid function test (T3, 1.3 nmol/L; free T4, 11.6 pmol/L; thyroid-stimulating hormone, 1.03 mU/L), and no specific abnormalities were detected on a physical examination of the neck. The patient had neither previously undergone a fine-needle biopsy for a thyroid lesion nor had a history of neck irradiation or surgery or a family history of a thyroid malignancy.A thyroid nodule that showed marked hypoechogenicity, an illdefined margin, and a taller-than-wide shape was identified in the left lobe on thyroid sonography. The nodule measured 5.5 mm in the maximal diameter and was considered to be highly suspicious for a malignancy (Fig 1A). A hypoechoic thyroid nodule that measured 1.0 mm in maximal diameter was detected in the medial aspect of the opposite right midlobe on a simultaneous diagnostic sonography examination, and this nodule was considered as an "indeterminate" nodule for a malignancy (Fig 1B). In addition, several thyroid nodules that showed benign sonographic features were observed in both lobes.A US-FNAB was performed by 1 investigator (D.W.K.) on the 2 nodules that showed a likelihood of being thyroid malignancies. Only 1 sampling was achieved for each thyroid nodule, without the administration of local anesthetic. A US-FNAB was not performed on several other thyroid nodules suggestive of being benign lesions on thyroid sonography because the selection of a nodule for US-FNAB was based primarily on the sonographic features rather than the nodule size. The patient had no significant pain or other complications following the US-FNAB procedure. On the basis of the cytology results, a nodule highly suspicious for a malignancy in the left lobe was identified as compatible with PTC (Fig 1C), and a 1-mm right-lobe nodule suspicious for a mal...
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