以Ki-67阳性指数行胰腺神经内分泌肿瘤细针穿刺细胞学分级及其与组织学分级的比较

Accurate grading of pancreatic neuroendocrine tumors with Ki-67 index in fine-needle aspiration specimens： a comparative cytologic and histologic study

目的 探讨以细针穿刺涂片的Ki-67阳性指数对胰腺神经内分泌肿瘤进行分级的可行性及准确性.方法 收集经组织学证实且行细针穿刺检查的胰腺神经内分泌肿瘤22例的病历资料、术后组织切片、细胞学涂片或细胞块切片.其中19例行术中穿刺,3例行超声内窥镜引导下细针穿刺.组织学标本及细胞学标本（每例选取肿瘤细胞总数〈200个的HE染色涂片1～2张或细胞块切片）,均采用免疫组织化学EnVision法检测Ki-67.按照WHO胃肠胰神经内分泌肿瘤三级分级系统进行分级,计数细胞学标本与组织学标本的Ki-67阳性指数和2类标本的分级结果符合率.将区分1级肿瘤与2级肿瘤的Ki-67临界值由2%提高到5%,或按照2013版中国胃肠胰神经内分泌肿瘤病理诊断共识推荐的500个肿瘤细胞为计数要求,比较两类标本的分级符合率变化.结果 胰腺神经内分泌肿瘤的细胞形态大多一致,异型性不明显,散在或排列成松散的细胞团,有菊形团样结构形成,部分病例中可见肿瘤细胞围绕薄壁毛细血管排列;肿瘤细胞具有特殊的胞质及胞核染色质分布特点;核分裂象及坏死罕见.以Ki-67阳性指数2%和20%为临界值分级,86.4%（19/22）病例细胞学分级与组织学分级一致,Kappa值为0.812（P〈0.01）.以5%和20%为临界值分级,分级符合率达到95.5%（21/22）,Kappa值为1.000（P〈0.01）.分别以200个和500个肿瘤细胞作为细胞量标准,分级符合率无明显差别.结论 胰腺神经内分泌肿瘤具有特征性的细胞学表现,在肿瘤细胞数〈200个的细胞学标本中,可以采用Ki-67阳性指数进行分级.在区分1级肿瘤与2级肿瘤时,以Ki-67阳性指数5%为临界值,细胞学与组织学标本的分级符合率更高.

Objective To study the cytomorphologic features and determine whether pancreatic neuroendocrine tumors （PanNET） sampled by fine-needle aspiration （FNA） can be accurately graded based on the Ki-67 index when compared to surgical samples.Methods Corresponding intraoperative （19 cases） or endoscopic ultrasound-guided （3 cases） FNA cytology and surgical tissue specimens were obtained from 22 tumors, which were reviewed and stained for Ki-67 proliferation marker.The cytological samples included more than 200 tumor cells.Samples were graded by scoring the Ki-67 positive index in accordance with the 2010 WHO criteria.The grading scores assigned to the FNA cytology samples were compared with the scores assigned to the corresponding histological samples.Concordance was achieved by using 5% （instead of 2%） as a cut-off value for defining G2 tumors.One cytological sample included less than 500 tumor cells was excluded in the concordance calculation.Results The cytological smears consisted of uniform, monotonous and isolated cells, loose cellular aggregates and rosette-like formations.Some tumor cells clustered around segments of capillaries.The cells demonstrated distinct cytoplasmic and nuclear features.Mitoses and necrosis were rarely seen.When traditional 2% Ki-67 index cut-off value were used to classify G2 tumors, the majority （86.4%,κ=0.812, P〈0.01） of FNA cytology samples and corresponding surgical tissue specimens demonstrated concordance.When a 5% cut-off value was adopted, the concordance rate was 95.5% （21/22, κ=1.000,P〈0.01）.Similar concordance rates between the cytological and histological grades were achieved with threshold value of cytological assessment material set at more than 500 or 200 cells.Conclusions The cytological Ki-67 index in adequate material （〉200 tumor cells） is useful in grading pancreatic neuroendocrine tumors, and a cut-off value of 5% showed better predictive value compared with that of 2%.Accurate grading of PanNET is critical for predicting tumor biology, patient prognosis, and making informed decisions regarding patient management and treatment.