A 52-year-old woman presented with complaints of anal pain/ constipation/tenesmus for 3 months before being referred to our hospital. There were no relevant prior illnesses. Rectal digital examinationrevealeda6-cmsmoothelasticmassontherectalposteriorleft side 2 cm from the anal verge. Colonoscopy showed a rectal submucosalbulging.Computedtomography(CT)scanandmagneticresonanceimagingconﬁrmedthepresenceofasingle6-cmwell-delimited mass, compressing and inﬁltrating the wall of the medium to low rectum. The tumor was completely removed, although ruptured, by transanal excision to save the organ. The specimen (2- to 22-mm fragments) was almost entirely composed of tumor, highly cellular andwithnecrosis,consistingofspindlecellswithperinuclearvacuolizationandseveralmitoses(80/50high-powerﬁelds;Fig1A,magniﬁcation 400). Scarce rectal wall smooth muscle was present (Fig 1B, left, magniﬁcation 100). The tumor stained for CD117 (Fig 1C, magniﬁcation 400), DOG1 (Fig 1D, magniﬁcation 400), CD34, and S100 (patchy cytoplasmic pattern); desmin, melan-A, and HMB45 were negative. The diagnosis was spindle-cell GI stromal tumor(GIST).Thepatient’sdiseasewasconsideredhigh-riskbecause ofthefragmentationduringremoval,morphology,andsite.1,2 Given thatasubsequentpositronemissiontomography/CTscanwasnegative,a conservativeapproachwasmaintained,leavingadditionalsurgeryasan option in case of relapse. By using polymerase chain reaction direct sequencing3-6onindependentDNAtemplatesfromfourdifferenttumor fragments, two mutations were consistently found: a 6-nucleotide– insertion GCCTAT between 1509-1510 nucleotides (CDS mutation: c. 1509_1510insGCCTAT)causinganinsertionoftwoaminoacids:alanine andtyrosine(p.Y503_F504insAY)inKITexon9(Fig2A;arrowindicates thestartpointoftheGCCTATinsertion),andapointmutation(A3Tat 2525)determiningaValforAspsubstitutionat842(D842V)ofexon18of platelet-derived growth factor receptor alpha (PDGFRA; Fig 2B; arrow indicatespointmutation).KITandPDGFRAwerewildtypeintherectal wallsmoothmuscle.