Journal of Modern OncologyJournal of Modern Oncology1815-14341815-1442LLC Obyedinennaya Redaktsiya7638510.26442/18151434.2021.4.201222Research ArticleMetastatic gastrointestinal stromal tumor of the greater omentum. Case reportYugayVladimir V.<p>oncologist</p>yugay_vladimir@mail.ruhttps://orcid.org/0000-0001-6169-2723NikulinMaxim P.<p>Cand. Sci. (Med.)</p>yugay_vladimir@mail.ruhttps://orcid.org/0000-0002-9608-4696MazurenkoNatalya N.<p>D. Sci. (Biol.), Prof.</p>yugay_vladimir@mail.ruhttps://orcid.org/0000-0003-4767-6983Mochal'nikovaValerija V.<p>pathologist</p>yugay_vladimir@mail.ruhttps://orcid.org/0000-0001-5275-7134FilonenkoDar'ja A.<p>Cand. Sci. (Med.)</p>yugay_vladimir@mail.ruhttps://orcid.org/0000-0002-7224-3111MeshherjakovAndrey A.<p>D. Sci. (Med.)</p>yugay_vladimir@mail.ruhttps://orcid.org/0000-0002-6009-653XBugaevVladislav E.<p>Cand. Sci. (Med.)</p>yugay_vladimir@mail.ruArhiriPetr P.<p>Cand. Sci. (Med.)</p>yugay_vladimir@mail.ruhttps://orcid.org/0000-0002-6791-2923StroganovaAnna M.<p>Cand. Sci. (Med.)</p>yugay_vladimir@mail.ruhttps://orcid.org/0000-0002-7297-5240StilidiIvan S.<p>D. Sci. (Med.), Prof., Acad. RAS</p>yugay_vladimir@mail.ruhttps://orcid.org/0000-0002-0493-1166Blokhin National Medical Research Center of OncologyYevdokimov Moscow State University of Medicine and DentistryLoginov Moscow Clinical Scientific CenterRussian Medical Academy of Continuous Professional EducationPirogov Russian National Research Medical University1512202123468068423072021Copyright © 2021, Consilium Medicum2021<p>Gastrointestinal stromal tumors (GIST) are the most common type of mesenchymal malignancies of the gastrointestinal (GI) tract. Almost 10% of them are originated outside of the GI tract (extra-GIST), while GIST of the greater omentum constitutes about 1% among stromal tumors. More than 80% of GIST have mutations in <em>c-KIT</em> and <em>PDGFRA</em> genes. Herein we demonstrate the case of successful treatment of patient with giant omental GIST with <em>c-KIT</em> exon 11 mutation. 64-years-old woman, was admitted to the Department of abdominal oncology with complaints of shortness of breath and abdominal enlargement in volume. CT-scan revealed a large tumor in the abdominal cavity with tumor size of 543422 cm. The patient underwent left thoraco-abdominal approach. It was found that the tumor was originated from the greater omentum with several metastases located on the peritoneum of the left lateral channel. Resection of the large omentum, splenectomy, liver resection and was done. Postoperative immunohistochemical study showed the expression of CD117, CD34 in tumor cells. Ki-67 index was 1215%. Genetic study revealed <em>c-KIT</em> exon 11 mutation. Treatment with imatinib 400 mg per day was started. Patient has been treated with imatinib for 12 years. On control examination we have found a metastasis in the anterior abdominal wall 3,532,5 cm in diameter. Afterwards we performed resection of anterior abdominal wall with metastasis on 9 November 2017. Immunohistochemical study confirmed metastasis of GIST. The index of tumor proliferation activity (Ki-67) was 45%. Patient prolonged imatinib treatment at the dose of 400 mg per day after operation. No signs of progression have been revealed on control examination 72 months after the operation. 12-year progression-free survival during imatinib treatment is unique in our practice. Moreover, in the case of further progression, we have second and third-line targeted therapy (sunitinib and regorafenib) and surgery treatment in local progression.</p>gastrointestinal stromal tumorextragastrointestinal stromal tumorgreater omentumGISTEGISTгастроинтестинальная стромальная опухольэкстраорганная гастроинтестинальная стромальная опухольбольшой сальникGISTEGIST[Fletcher C, Berman J, Corless C, et al. Diagnosis of gastrointestinal stromal tumors: A consensus approach. Hum Pathol. 2002;33(5):459-65. DOI:10.1177/106689690201000201][Kindblom LG, Remotti HE, Aldenborg F, et al. Gastrointestinal pacemaker cell tumor (GIPACT): gastrointestinal stromal tumors show phenotypic characteristics of the interstitial cells of Cajal. Am J Pathol. 1998;152(5):1259-69.][Patil D, Rubin B. Genetics of Gastrointestinal Stromal Tumors: A Heterogeneous Family of Tumors? Surg Pathol Clin. 2015;8(3):515-24. DOI:10.1016/j.path.2015.05.006][Sakurai S, Fukasawa T, Chong J, et al. C-KIT Gene Abnormalities in Gastrointestinal Stromal Tumors (Tumors of Interstitial Cells of Cajal). Japanese J Cancer Res. 1999;90(12):1321-28. DOI:10.1111/j.1349-7006.1999.tb00715.x][Mouaqit O, Jahid A, Ifrine L, et al. Primary omental gastrointestinal stromal tumors. Clin Res Hepatol Gastroenterol. 2011;35(8-9):590-3. DOI:10.1016/j.clinre.2010.11.012][Mei L, Smith S, Faber A, et al. Gastrointestinal Stromal Tumors: The GIST of Precision Medicine. Trends Cancer. 2018;4(1):74-91. DOI:10.1016/j.trecan.2017.11.006][Yamamoto H, Oda Y, Kawaguchi K, et al. C-KIT and PDGFRA Mutations in Extragastrointestinal Stromal Tumor (Gastrointestinal Stromal Tumor of the Soft Tissue). Am J Surg Pathol. 2004;28(4):479-88. DOI:10.1097/00000478-200404000-00007][Reith J, Goldblum J, Lyles R, et al. Extragastrointestinal (Soft Tissue) Stromal Tumors: An Analysis of 48 Cases with Emphasis on Histologic Predictors of Outcome. Mod Pathol. 2000;13(5):577-85. DOI:10.1038/modpathol.3880099][Miettinen M, Monihan J, Sarlomo-Rikala M, et al. Gastrointestinal Stromal Tumors/Smooth Muscle Tumors (GISTs) Primary in the Omentum and Mesentery. Am J Surg Pathol. 1999;23(9):1109. DOI:10.1097/00000478-199909000-00015][Yi JH. Retrospective analysis of extra-gastrointestinal stromal tumors. World J Gastroenterol. 2015;21(6):1845. DOI:10.3748/wjg.v21.i6.1845][Li ZY, Huan XQ, Liang XJ, et al. Clinicopathological and immunohistochemical study of extra-gastrointestinal stromal tumors arising from the omentum and mesentery. Zhonghua Bing Li Xue Za Zhi. 2005;34(1):11-4.][Wong N. Gastrointestinal stromal tumours – an update for histopathologists. Histopathology. 2011;59(5:807-21. DOI:10.1111/j.1365-2559.2011.03812.x][Gun B, Gun M, Karamanoglu Z. Primary Stromal Tumor of the Omentum: Report of a Case. Surgery Today. 2006;36(11):994-6. DOI:10.1007/s00595-004-3280-9][Dimofte MG, Porumb V, Ferariu D, et al. EGIST of the greater omentum – case study and review of literature. Rom J Morphol Embryol. 2016;57(1):253-8.][Sakurai S, Hishima T, Takazawa Y, et al. Gastrointestinal stromal tumors and KIT-positive mesenchymal cells in the omentum. Pathol Intern. 2001;51(7):524-31. DOI:10.1046/j.1440-1827.2001.01224.x][Miettinen M, Lasota J. Gastrointestinal stromal tumors – definition, clinical, histological, immunohistochemical, and molecular genetic features and differential diagnosis. Virchows Archiv. 2001;438(1):1-12. DOI:10.1007/s004280000338][Agaimy A, Wünsch P. Gastrointestinal stromal tumours: a regular origin in the muscularis propria, but an extremely diverse gross presentation. Langenbeck’s Arch Surg. 2006;391(4):322-9. DOI:10.1007/s00423-005-0005-5][Miettinen M, Sobin L, Sarlomo-Rikala M. Immunohistochemical Spectrum of GISTs at Different Sites and Their Differential Diagnosis with a Reference to CD117 (KIT). Mod Pathol. 2000;13(10):1134-42. DOI:10.1038/modpathol.3880210]