Study On Clinicopathological Characteristics And Genetic Variation Of Special Gastrointestinal Stromal Tumors

Part Ⅰ Study on clinicopathological features of gastrointestinal stromal tumor and relevant prognostic factorsBackground: Due to the fact that 20%–30 % of gastrointestinal stromal tumor（GIST）are malignant and 11%–47 % of patients show metastases at the first clinical visit,the study on prognostic factors has significant implications for GIST treatment.Objective: The objective of the study is to investigate and analyze clinicopathological features of GIST and relevant prognostic factors.Methods: Between September 2008 and April 2014,168 patients who presented with pathologically confirmed GIST and underwent surgical resection of the tumors in our institution were included in this study.A retrospective study on clinicopathological features of the disease and follow-up study on 1-year,3-year,and 5-year survival rates were performed.Results: Of 168 patients,113 were males and 55 females of age ranging from 18 to 78 years.Common symptoms of GIST include abdominal pain and blood stools.Of all patients,115（68.4 %）developed tumors in GI tract,51（30.4 %）presented multiple tumors,88（52.4 %）tumors displayed a maximal diameter >5 cm,mitotic count ≥5/50 HPF were observed in 80 patients.Positive rate of CD117 was 92.9 %（156/12）,DOG1 97.0 %（163/5）,CD34 53.0 %（89/79）and S-100 25.6 %（43/125）.Follow-up study achieved in 149 patients.Survival analysis and Cox regression analysis demonstrated that no significant prognostic effects were observed for gender,clinical presentations,tumor location,number of tumors,CD34 and S-100 expression（p>0.05）.However,tumor diameter and mitotic count were factors with significant effect on prognosis of GIST（p<0.05）.Tumors with diameter >5 cm and mitotic count ≥5/50 HPF resulted in poor prognosis.Conclusion: Tumor diameter and mitotic count are helpful for the evaluation of prognosis with favorable clinical value in GIST.Part Ⅱ Study on rare molecular genetic and pathological characteristics of classical mutant GISTBackground: Gene mutation of GIST mainly occurs in the KIT proto-oncogene and PDGFRA gene mutation was found in a few of them.Is there any other known and unknown gene mutation?Objective: In this part,we investigated rare types besides common types of KIT gene and PDGFRA gene,and their corresponding clinicopathological characteristics.Methods: We retrospectively analyzed a cohort of 96 cases with pre-imatinib,primary localized and operable GIST,tested by next-generation sequencing,from July 2010 to August 2017.Tumor morphology,immunohistochemistry,risk,treatment,and patient follow-up were examined.Results: Among 96 cases,80 had KIT gene mutation and 4 had PDGFRA gene mutation.There were 84 cases of classic mutant GIST,44 males and 40 females,age ranging from 38 to 70 years,with and average age of 64 years.1)Among the 80 KIT mutations,64 had exon 11 mutations,mainly deletion mutations,including codon 555-559,576 and 557-558.The rare mutant types included 576 and 557 substitution mutations.At the same time,there were other rare mutant genes,namely FLT1 gene substitution mutation,DDR2 gene substitution mutation.There were nine cases in exon 9,including five cases of duplication mutation（codons 502–503）,three cases of insertion mutation（codon 501）,and one case of substitution mutation（N486K）.Additionally,the substitution mutation case showed a novel synchronous CCNYL1–BRAF rearrangement.The fusion mutation case was a mixed cell form,with a unique meningioma-like vortex structure.There were four cases in exon 13,all of which were substitution mutations（K642E）,and three cases（3/16）in exon 17,all of which were substitution mutations（N822K）.2)PDGFRA gene mutation in 4 cases,3 cases were located in exon 18.In addition to the common D842 V mutation type,codon 843 insertion mutation and codon 842-845 deletion mutation were firstly found,combined with DDR2 gene substitution mutation;only one case had codon 561 substitution mutation in exon 12 of PDGFRA.Conclusion: There are rare gene mutant types in classic GIST.At the same time,new fusion genes and new mutant genes can be combined with the common KIT or PDGFRA gene.These mutations may be related to special histological types and tumor prognosis.Part Ⅲ Study on molecular genetic and pathological characteristics of rare classical mutant GISTBackground: Primary GIST outside the digestive system is rare,including regional lymph node metastasis and bone metastasis.The most common site of metastasis is the liver,and a small number of patients with metastasis as the first symptom.GIST can be combined with other tumors,especially digestive system tumors.In addition,GIST can be used targeted therapy.Does targeted therapy affect gene mutation types and pathological characteristics?Objective: This part is to discuss the clinicopathological and molecular genetic characteristics of the rare special types of classic mutant GIST（GIST with lymph node metastasis,GIST with bone metastasis,GIST with primary extra-gastrointestinal tract,GIST with digestive system tumor,GIST after targeted treatment）.Methods: We retrospectively analyzed a cohort of 264 cases（from Part I and Part II）,and the corresponding clinical and pathological information was collected.The mutation types of KIT gene and PDGFRA gene were detected and analyzed by the first-generation sequencing technology.Meanwhile,the tumor morphology,immunophenotype,risk,treatment methods,etc.were analyzed,and the patients were followed up.Results: There were 9 cases of primary extra-digestive system（EGIST）,2 males and 7 females,aged 28-72 years old,most of them were retroperitoneal,and the features of morphology,immunohistochemistry and gene mutation were similar to those of GIST in digestive system;there were 14 cases of small GIST with digestive system tumor,8males and 6 females,aged 48-82 years old.The small GIST was mainly found in stomach.The tumor cells were sparse,and most of them had KIT gene mutation.There were 6 cases of GIST with lymph node metastasis,5 cases of male and 1 case of female,and the age span was 48-75 years.Almost all of them had simultaneous liver metastasis and spread in the abdominal cavity.KIT gene mutation was found in 6 cases;3 cases with rare bone metastasis were found in esophagus,stomach and small intestine.Bone metastasis mainly occurred in pyramidal bone and humerus,all of them had KIT gene mutation;the tumor of 1 case with rare simultaneous bone and lung metastasis GIST after targeted treatment,female,71 years old,had multiple necrosis and swelling.Also,part of the tumor cells showed rhabdomyoid morphology.Conclusion: The judgment criteria of EGIST is the same as classic GIST in terms of pathological characteristics,genetic characteristics and biological behavior.The small GIST with digestive system disease has a very low risk,which suggests that it may be an early rising event of GIST.The mutant GIST with lymph node metastasis often has a high risk,as well as the simultaneous liver and abdominal cavity metastasis.Most of them have mutation in exon 11 of KIT gene.GIST with bone metastasis is most located at spine,with high risk,especially combined with liver metastasis.GIST with rare bone and lung metastasis after targeted therapy often has morphological changes.Part Ⅳ clinicopathological and molecular genetic characteristics of wild-type GISTBackground: Most of the wild-type GIST have SDH deletion mutation,BRAF gene mutation,and so on.Are there other mutation genes and mutation types?Objective: In this part,we want to explore whether there are rare mutations besides the common types of gene mutations of wide type GIST,and their clinicopathological characteristics of the mutations.Methods: From July 2010 to August 2017,96 cases of localized GIST were analyzed retrospectively.The clinical and pathological information was collected.First,the first generation sequencing technology was used to screen wild-type GIST,and the next generation sequencing（NGS）technology was used to further select these tumors and analyze whether there were known or unknown gene mutation types;at the same time,tumor morphology,immunophenotype,risk and treatment methods were analyzed,and patients were followed up.Results: Of the 96 cases of GIST,12 were wild-type,7 were female,5 were male,aged 36-82 years.Five of them were SDH deficient GIST,and the immunohistochemistry showed that the expression of SDHB was absent,most of them were female,all of them occurred in the stomach,histology was mainly epithelioid;molecular detection found that one case had the substitution mutation of SDHA gene（E564K）,the amplification mutation of CCND1 and RB1 gene,and the tumor showed malignant characteristics;another case had the substitution mutation of SDHD gene（D113Tfs₂2）,and the substitution mutation of TP53 gene（D281Y）.In another case,there were two different mutations of TP53 gene,substitution mutation（R273H）and deletion insertion mutation（300₃08）,and p53 protein was diffuse positive expression,the tumor presented malignant behavior.There were 7 cases of non-SDH deficient GIST,2 of them had BRAF gene substitution mutation（V600E）,and the corresponding protein（BRAFV600E）was positive expression,all of them were spindle cell type,one of them occurred in micro GIST with tumor volume of 0.6cm;another case had CDH1 gene functional germline mutation,the mutation type was substitution mutation（D786N）,the tumor was primary in duodenum,with high proliferation index（20%）and high risk.Conclusion: In wild-type GIST,there are rare mutation types,such as TP53 gene mutation,CCND1 gene amplification,RB1 gene amplification,which can be combined with SDH gene subunit mutation.Some gene mutations may be related to the malignant biological behavior of tumors.In non-SDH deficient GIST,in addition to the common BRAF gene mutation,there are rare CDH1 gene mutation,which may also be related to the invasive biological behavior of tumors.