| Objective:To study the clinicopathologic parameters of pancreatic endocrine tumors (PETs), examined the expression of CD99 in PETs and analysed the correlation with clinicopathologic parameters, investigated the value of CD99 in predicting biological behavior and clinical prognosis of PETs.Methods:To analyze the clinicopathologic parameters of 34 PETs, including tumor size, functional status, histological classification, local invasion or metastasis, mitoses and so on. Immunohistochemical method was used to examine the expression of CD99, Insulin, Ki-67 in PETs, and follow-up was undertaken with the patients. Evaluating the correlation between expression of CD99 and clinicopathologic features. Calculations and analyses were performed by using SAS 8.1 statistics software. Adopting Fisher Exact Test to determine the association between expression of CD99 and the selected variables.Results:1. Association between tumor size and the expression of CD99:The average size of 16 cases which CD99 negative/low expression is 3.2 cm, 5 cases measuring≥3 cm. The average size of tumors which CD99 positive is 2.2 cm (overall series mean:2.7 cm). The tumors which CD99 negative/low expression were obviously bigger than CD99 positive ones. However, tumor size showed no statistical association with CD99 expression. Of the 34 PETs,8 tumors (23.5%) were more than 3 cm in size. Of the cases measuring≥3cm,3 had an adverse outcome,4 living well. Of the cases measuring <3cm, all 18 had a follow-up currently alive and free of disease. The tumor size was correlated with prognosis (P=0.0152), a smaller tumor prognosticated a well prognosis.2. Association between local invasion or metastasis and the expression of CD99:Of the 34 PETs,18 cases (53%) were CD99-positive,17 of the 25 cases confined to the pancreas and lacking aggressive clinicopathologic criteria were CD99-positive.5 cases with local invasion (including the 2 lymph node spread) were all CD99-negative; 1 with spleen and liver metastases showed less than 30% of the tumor population being CD99-positive. CD99 negative/low expression was significantly correlated with gross local invasion and metastasis of the PETs (P=0.006).5 of the 6 cases with local invasion or metastases had a follow-up, only 2 cases had local invasion but no metastases were living well. All 3 cases with metastases (including 2 lymph node spread and 1 spleen and liver metastases) had an adverse outcome (death or recurrence).3. Association between functional status of the tomors and the expression of CD99:18 CD99-positive cases were all Insulin-positive,14 cases had obvious hormone symptoms. Of 16 CD99-negative cases,10 were functioning tumors, and 6 non-functioning tumors. There was no statistical association between CD99 expression and functional status of the tomors.37.5%(3 of the 8) non-functioning tumors had an adverse outcome (death or recurrence), while all followed up patients with insulinoma were living well. The prognosis of non-functioning PETs was obviously worse than functioning PETs.4. Association between mitoses and the expression of CD99:27 cases mitoses<2/10HPF,6 cases mitoses 2～10/10HPF, and 1 case mitoses> 10/10HPF. There was no statistical association between CD99 expression and mitoses. It was noting that all 3 cases with metastases and had an adverse outcome mitoses≥2/10HPF, including 1 death mitoses>10/10HPF.5. Association between Ki-67 index and the expression of CD99:Of the 34 PETs,12 cases Ki-67 index>2%, including 6 cases Ki-67 index≥5%,22 cases Ki-67 index≤2%. There was no statistical association between CD99 expression and Ki-67 index. All 3 cases had an adverse outcome Ki-67 index >2%, including 2 cases Ki-67 index≥5%, but of the other 4 cases with Ki-67 index≥5%, all 3 cases had a follow-up were living well, and lacking aggressive clinicopathologic criteria. Therefore, Ki-67 index could not to be an independent prognostic predictor of PETs.6. Association between the expression of CD99 and prognosis:14 of the 18 CD99-positive PETs were living well (follow-up period of 11 cases was more than 2 years).1 death and 2 recurring cases were CD99-negative/low expression. CD99 loss/low expression may correlated with a poor prognosis of the PETs. However, in view of only a few cases, no real meaningful comment can be made regarding patient survival and CD99 expression.Conclusion:The biological behavior of PETs is difficult to predict based on their histologic features. Metastasis is generally accepted to be the only definitive feature of malignancy. Tumor size, functional status of the tomors, local invasion or metastasis, mitoses and Ki-67 index were all related with the prognosis. This study confirms that the expression of CD99 was significantly correlated with the behavior of PETs. CD99 loss/low expression was correlated with malignant progression and a poor prognosis of the PETs. It may proved to be an important prognostic predictor of PETs. |
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