The Clinicopathorlogic Characteristics Of Metastasic Gastrointestinal Stromal Tumors

ObjectTo explore clinicopathologic characteristics of metastatic gastrointestinal stromal tumors ( GISTs), especially the mechanism of lymph node metastasis.MethodsConfirmed cases of GIST were retrieved for a total number of 1080 cases,including consultation specimens of 68 cases, rapid specimens of 176 cases, frozen specimens of 11 cases, surgical specimens of 825 cases from the pathology disciplines of Anhui medical university during November 2011 - October 2016. We selected 46 cases of surgical specimens with metastasis for the research including 9 cases of lymph node metastasis, 12 cases of liver metastasis, 25 cases of abdominal cavity metastasis.50 cases of primary tumors belong to the same period were contained to comparison.All materials were stained with HE staining and immunohistochemical method that marked CD117, CD34 , SMA, DOG - 1, S - 100, Ki - 67, CD31, D2-40,SDHB and then observed all sections and calculated the Ki - 67 proliferation index, mitotic figures per 50 HPFs, MVD and LMVD of tumors within the parenchyma, the tumor edge and the surrounding "normal tissue" were calculated.Results1) The total metastatic rate was 5.5%, the blood metastatic rate was 1.5% and the lymph node metastatic rate was 1.0%.2) MVD of metastatic GIST is 398.00±68.20/mm2 and non-metastatic GIST is 192±56.85 /mm2, the difference between them is statistically significant.MVD of lymph node metastatic GIST is 515.00±72.20 /mm2 and MVD of metastatic GIST exclude lymph node metastasis is 353.00±32.20/mm2, the difference between them is statistically significant.3) There is no lymphatic vessels distribution in the parenchyma of GIST. About metastatic GIST ,LMVD of the edge area of the parenchyma is 13.00±2.40 /mm2 and LMVD of "normal tissue" around the parenchyma is 25.00±6.70/mm2. In regard to non-metastatic GIST, LMVD of the edge area of the parenchyma is 12.00±1.80 /mm2 and LMVD of "normal tissue" around the parenchyma is 24.00±8.60/mm2.No statistically significant exists between LMVD of the edge area of the parenchyma and LMVD of "normal tissue" around the parenchyma.4) Mitotic figures of lymph node metastatic GIST is 22/50HPFs ,nevertheless mitotic figures of non- metastatic GIST is 4/50HPFs, the difference between them is statistically significant.5) The Ki - 67 proliferation index of lymph node metastatic GIST is 0.18 but mitotic figures of non- metastatic GIST is 0.05, the difference between them is statistically significant.6) 8 from 9 cases of GIST with lymph node metastasis and 12 from 86 cases of non-metastatic GIST proliferate in invasive growth way.7) Of the 9 cases of lymph node metastasis GISTs,8 cases of them were SDHB negative and 1 case was weakly positive so that the lymph node metastatic GIST was absent in the SDHB expression.Conclusion1 )MVD of metastatic GIST is significantly higher than that of non-metastatic GIST.2) There is no lymphatic vessels within the tumor parenchyma, and that can explain the rare lymph node metastasis.3 ) Lymph node metastatic GIST proliferate in invasive growth way and this may be the reason of lymph node metastasis.4) There is a lack of SDHB expression in lymph node metastatic GIST and that is instructive to determine whether lymph node resection is performed in clinical surgery.