Follicular variant of papillary thyroid carcinoma:analysis of sonographic features and misdiagnosis / 中华医学超声杂志（电子版）

ABSTRACT

Objective To investigate the sonographic features of follicular variant of papillary thyroid carcinoma (FV-PTC) and to decrease misdiagnosis rate. Methods Thirty-one patients with 35 FV-PTCs and 66 patients with 75 conventional PTCs (C-PTCs) were enrolled in this study. The sonographic features were reviewed retrospectively between the two groups with universally accepted standards. Results The sonographic features of 35 FV-PTCs included irregular shapes (6/35), anteroposterior to transverse diameter ratio A/T > 1 (7/35), spiculated margins (25/35), marked hypoechogenicity (0/35), hypoechogenicity (18/35), isoechogenicity (16/35), no calcification (15/35), microcalcifications (11/35), macrocalcification (9/35), color Doppler lfow patternⅠ(20/35), color Doppler lfow patternⅡ(10/35), color Doppler lfow patternⅢ(5/35). Irregular shapes, A/T>1, spiculated margins, marked hypoechogenicity, microcalciifcations, and color type Ⅱ were rarer in FV-PTCs than in C-PTCs, while isoechogenicity, no calciifcation, macrocalciifcation, and color type Ⅲwere more frequent in FV-PTCs than in C-PTCs. The differences of the above features were statistically significant [χ2=4.276, P=0.039; χ2=8.125, P=0.004; P=0.009 (Fisher′ s exact test); χ2=8.548, P=0.003;χ2=4.898, P=0.027,χ2=7.796, P=0.005;χ2=5.462, P=0.019;P=0.001 (Fisher′s exact test)] . During the preoperative ultrasonography, 20 of 35 FV-PTCs were diagnosed as malignancy, and others were misdiagnosed as benign nodules (misdiagnosis rate was 43%). The lymphatic metastasis rate of FV-PTCs was 29%(9/31), significantly lower than C-PTCs [62%(41/66),χ2=9.246, P=0.002]. In terms of the sonographic features of metastatic lymph nodes, there was no marked difference between FV-PTCs and C-PTCs. Conclusions Some FV-PTCs are lack of malignant features, and tend to be misdiagnosed frequently when coexisting with benign thyroid nodules. Observing the echogenicity, color lfow characteristics and other features of each thyroid nodule and cervical lymph node with multiple views may decrease the misdiagnosis rate.