Cytologic Features of Thyroid Lesions Diagnosed as Indeterminate for Neoplasia Which Predict Follicular Neoplasm on Fine Needle Aspiration Biopsy of Thyroid (FNAB): A 5-Year Retrospective Study in a Tertiary Care Hospital in Ontario, Canada

IT Ahmed, KT Mai, S Islam. The Ottawa Hospital, The University of Ottawa, Ottawa, ON, Canada.

Background: Follicular lesions (FL) of the thyroid encompass non-neoplastic and neoplastic lesions. Diagnosis of follicular lesion is a challenging area in the interpretation of thyroid FNAB. Objectives: The purpose of the study is two-folds: 1). To identify cytologic features that will more accurately predict neoplasia (FN) and 2). To recognize diagnostic pitfalls in the differential diagnosis of follicular lesions (FL).

Design: A computer database search was performed for FL, indeterminate for neoplasia on FNAB of thyroid between January 2003 and August 2008 from the archives of the Cytopathology section at our institution. A total of 504 cases were retrieved with a diagnosis of FL; 205 (40.6%) had a histological follow-up and were retained for the study.

Results: Histological follow-up of 205 cases showed follicular Adenoma (FA) in 53 (25.8%), hurthle cell adenoma (HA) in 19 (9.2%), multi-nodular goitre (MGN) in 95 (46.3%), papillary carcinoma, follicular variant (PTCFV) in 25 (12.2%), thyroiditis (THY) in 8 (3.9%) and follicular carcinoma (FC) in 5 (2.4%) patients. Cytologic features that accurately predict FA (48 specimens, 91%), FC (4 specimens, 80%) and PTCFV (23 specimens, 92%) are tight microfollicle formations (defined as acinar structures formed by crowed enlarged nuclei with chromatin clearing and inconspicuous nucleoli) present in >60% of the smears and scant to nil colloid. Another important cytological fearture than we found in our study is the presence of nuclear grooves in more than 5% of follicular cells, which predicts presence of neoplastic lesion. However, presence of nuclear grooves in more than 30% of follicular cells are predictive of papillary carcinoma. Nuclear grooves in more than 5% of follicular cells were found in FA (16 specimens, 30%), FC (2 specimens, 40%) and PTCV (16 speicmens,64%) on FNAB. The most common diagnostic pitfall is follicular cells wrapped up in clotted blood and endothelial cells (MGN, 87 specimens).

Conclusions: The cytologic features that will increase diagnostic specificity of FN (FA, FC and PTCFV) are tight microfollicle formations present in more than 60% of the smears, nuclear grooves in >5% of cells and scant colloid. The most common diagnostic pitfall is clotted blood.

Cytologic Features of Thyroid Lesions Diagnosed as Indeterminate for Neoplasia Which Predict Follicular Neoplasm on Fine Needle Aspiration Biopsy of Thyroid (FNAB): A 5-Year Retrospective Study in a Tertiary Care Hospital in Ontario, Canada

 甲状腺的细胞学特征作为滤泡性肿瘤在甲状腺细针穿刺活检诊断中的依据并不确定：加拿大，安大略湖，Tertiary Care 医院，一份5年的回顾性研究证实。

Background: Follicular lesions (FL) of the thyroid encompass non-neoplastic and neoplastic lesions. Diagnosis of follicular lesion is a challenging area in the interpretation of thyroid FNAB. Objectives: The purpose of the study is two-folds: 1). To identify cytologic features that will more accurately predict neoplasia (FN) and 2). To recognize diagnostic pitfalls in the differential diagnosis of follicular lesions (FL).

背景：围绕着甲状腺滤泡性病变的非肿瘤性和肿瘤性病变，在甲状腺细针穿刺活检术的诠释中，滤泡性病变诊断是一个充满挑战的领域。目标：研究的目的如下两方面;1)更多明确的细胞病理学特征将用于细针穿刺中肿瘤的描述。2）认识在滤泡性肿瘤的鉴别诊断的诊断陷阱

Design: A computer database search was performed for FL, indeterminate for neoplasia on FNAB of thyroid between January 2003 and August 2008 from the archives of the Cytopathology section at our institution. A total of 504 cases were retrieved with a diagnosis of FL; 205 (40.6%) had a histological follow-up and were retained for the study.

设计：滤泡性肿瘤的信息可以在电脑数据库中查找，在我们的机构中有来自2003.1--2008.8的甲状腺细针穿刺活检术不能确诊的细胞病理学档案，共有504例被诊断为滤泡性肿瘤，其中205例（40.6%）有组织病理学追踪随访以便保留用于研究

Results: Histological follow-up of 205 cases showed follicular Adenoma (FA) in 53 (25.8%), hurthle cell adenoma (HA) in 19 (9.2%), multi-nodular goitre (MGN) in 95 (46.3%), papillary carcinoma, follicular variant (PTCFV) in 25 (12.2%), thyroiditis (THY) in 8 (3.9%) and follicular carcinoma (FC) in 5 (2.4%) patients. Cytologic features that accurately predict FA (48 specimens, 91%), FC (4 specimens, 80%) and PTCFV (23 specimens, 92%) are tight microfollicle formations (defined as acinar structures formed by crowed enlarged nuclei with chromatin clearing and inconspicuous nucleoli) present in >60% of the smears and scant to nil colloid. Another important cytological fearture than we found in our study is the presence of nuclear grooves in more than 5% of follicular cells, which predicts presence of neoplastic lesion. However, presence of nuclear grooves in more than 30% of follicular cells are predictive of papillary carcinoma. Nuclear grooves in more than 5% of follicular cells were found in FA (16 specimens, 30%), FC (2 specimens, 40%) and PTCV (16 speicmens,64%) on FNAB. The most common diagnostic pitfall is follicular cells wrapped up in clotted blood and endothelial cells (MGN, 87 specimens).

结果：组织病理学追踪显示205例中滤泡性腺瘤（FA)为53例（25.8%），嗜酸细胞性腺瘤(HA)为19例（9.2%），多结节性甲状腺肿(MGN)为95例（46.3%）乳头状癌滤泡亚型（PTCFV)为25例（12.2%），甲状腺炎（THY）为8例（3.9%）滤泡癌（FC）为5例（2.4%），在确诊为FA（48例，91%），FC（4例，80%）和PTCFV(23例，92%）的60%以上的病例中以及缺乏胶质的样品中可见有明显的微滤泡排列结构的细胞学特征（腺泡结构的表现为染色质清晰和核仁不明显的聚集成团的细胞）在我们的研究中发现了另一个重要的细胞学特征是在确诊为肿瘤的病变中超过5%的滤泡细胞出现核凹陷，不过在确诊为乳头状癌的病例中超过30%的滤泡细胞也同样出现核凹陷，在细针穿刺活检术中FA（16例，30%）,FC（2例，40%）,PTCV（16例，30%）中有超过5%的滤泡细胞出现核凹陷。最常见的诊断陷阱是滤泡细胞被隐藏在血凝块和上皮细胞内（MGN,87例样品）

 Conclusions: The cytologic features that will increase diagnostic specificity of FN (FA, FC and PTCFV) are tight microfollicle formations present in more than 60% of the smears, nuclear grooves in >5% of cells and scant colloid. The most common diagnostic pitfall is clotted blood

结论：如下的细胞病理学特征可以提高甲状腺细针穿刺活检术的诊断率，紧密的微滤泡结构出现在超过60%的样品中，超过5%的细胞出现核凹陷以及胶质缺乏，最常见的诊断陷阱是血凝块