Gastrointestinal Stromal Tumor: Chondro-Myxoid Variant Mimicking Chondrosarcoma

SW, an 84-year-old African American female,presented to an outside institution complaining ofdull, intermittent abdominal pain in the anterolateraland suprapubic regions. Decreased appetite, nausea,and general weakness accompanied this pain.Physical exam revealed a soft, non-tender mass inthe left upper quadrant that extended 20cm belowthe costal margin. A separate 2cm mass, in theperiumbilical area, was also palpable. A CT scan(Figure 1) was performed and revealed a large, softtissue mass in the left upper quadrant extending fromthe gastroesophageal junction to the mid-abdomen.The mass seemed to originate from the stomachcompressing the stomach medially, and the pancreasand spleen inferiorly and laterally. The periumbilicalmass was subcutaneous and separate from thelarger mass. A fine needle aspiration and biopsyof the umbilical mass was diagnosed as a myxoidchondrosarcoma. No further therapy was given atthat time.Approximately four months later, the patientpresented to our institution with nausea, abdominalpain, and increased regurgitation of food. Given theclinical presentation, radiologic findings, and biopsyresults, the patient was felt to have a primary sarcomaof the stomach. Since the patient was an appropriatesurgical candidate, she was taken to the operatingroom. Upon laparotomy, a large mass, originatingfrom a pedicle attached to the greater curvatureof the stomach, was observed. The tumor wasadherent to the diaphragm and to the lateral segmentof the liver. No invasion of any other adjacentstructures was observed. The periumbilical massappeared to be a portion of the original tumor thathad become incarcerated in an umbilical herniadefect that had fractured away from the dominantlesion.On gross pathologic examination, a 7012 gram,multinodular, cerebreform mass, was observed to bearising from within the wall of the greater curvatureof the stomach. This mass extended from nearthe gastroesophageal junction to the pyloris. Thetumor showed expansive intra-abdominal growthand involved the omentum and anterior abdominalwall. Sectioning showed a heterogeneous, lobulated,gray-white mass with areas of necrosis, hemorrhage,and cystic degeneration (Figure 2).The tumor had a variable histologic appearance.Portions of the tumor were relatively hypocellularwith a vaguely nodular, but prominent chondroidmatrix. Dispersed within this matrix were discohe-sive epithelioid cells. Focal areas of myxoid cysticdegeneration were also present. The majority ofthe tumor was extremely cellular containing sheetsof epithelioid cells within a chondroid matrix.Additionally, other areas had more spindle-shapedcells. These cells showed nuclear palisading andwere aligned in a perivascular distribution. Focally,these cells formed microcysts. Tumor cell necrosis,hemorrhage, and high mitotic activity (65/50hpf) wasobserved in these spindle cell areas. The differentialdiagnosis of this tumor upon H&E staining includeda chondrosarcoma and a gastrointestinal stromaltumor (Figure 3). S100 staining, which should bepositive in >95% of chondrosarcomas, was negative.The tumor cells were positive for c-kit (CD-117),CD-34, CD-99 (mic2), and smooth muscle actin(SMA) (Figure 3). This staining pattern confirmed