title: GIST Manifesting as a Retroperitoneal Tumor: Clinicopathologic Immunohistochemical, and Molecular Genetic Study of 112 Cases.
abstract: Most gastrointestinal stromal tumors (GISTs) occur in the tubular gastrointestinal (GI) tract, but some present apparently outside the GI tract. In this study, we analyzed 112 GISTs located in the retroperitoneum. These tumors occurred in 55 women and 57 men with a median age of 65 years (range: 21 to 89 y). On the basis of clinically or histologically detected connections to GI tract, 15 tumors were considered likely of gastric, 9 duodenal, and 13 of small intestinal origin. The remaining cases were categorized by location as peripancreatic (n=25), pelvic (n=11), mesenteric (n=4), and of unspecified/miscellaneous sites (n=35). The tumors varied in size 3 to 35 cm (median, 15 cm) and by mitotic rate per 5 mm, 0 to >100 (median, 10). Histologically the tumors apparently arising outside the GI tract had features of intestinal (n=41) and gastric GISTs (n=25); 9 cases had indeterminate histology. The histologic variants included spindled, epithelioid, vacuolated, nested, and myxoid potentially simulating other tumors such as liposarcoma and solitary fibrous tumor. Most GISTs were KIT-positive (106/112 cases), and the remaining 6 tumors were DOG1/Ano1-positive. Five cases showed focal nuclear positivity for MDM2. KIT mutations were detected in 42/59 cases, and PDGFRA mutations in 4/16 KIT wild-type and 3/5 of the KIT-negative tumors analyzed. One pelvic retroperitoneal GIST was succinate dehydrogenase deficient. All 79 patients were dead at last follow-up with a median survival of 14 months, with few survivals >5 years. Only operable versus inoperable tumor was a statistically favorable factor in univariate analysis (P<0.01). In multivariate analysis, mitotic rate >50/5 mm was significant for a shorter survival (hazard ratio, 5.25; 95% confidence interval, 1.65-16.8; P<0.01). Histologic and clinicopathologic similarity of extragastrointestinal retroperitoneal GISTs with GISTs of GI tract suggests their GI tract origin. Potentially overlapping features between GIST and other retroperitoneal tumors necessitate use of multiple diagnostic markers and molecular genetic studies.
authors.affiliation: *Laboratory of Pathology, National Cancer Institute, Bethesda, MD †Aichi Medical University School of Medicine, Nagakute, Japan.
authors.forename: Markku
authors.initials: M
authors.lastname: Miettinen
authors.forename: Anna
authors.initials: A
authors.lastname: Felisiak-Golabek
authors.forename: Zengfeng
authors.initials: Z
authors.lastname: Wang
authors.forename: Shingo
authors.initials: S
authors.lastname: Inaguma
authors.forename: Jerzy
authors.initials: J
authors.lastname: Lasota
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000075369:Anoctamin-1; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics*; D001706:Biopsy; D018118:Chloride Channels / Q000032:analysis; D004252:DNA Mutational Analysis; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000737:chemistry / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D020022:Genetic Predisposition to Disease; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D008940:Mitotic Index; D025202:Molecular Diagnostic Techniques; D015999:Multivariate Analysis; D009154:Mutation; D009363:Neoplasm Proteins / Q000032:analysis; D010641:Phenotype; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis / Q000235:genetics; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000235:genetics; D012186:Retroperitoneal Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D012307:Risk Factors; D013385:Succinate Dehydrogenase / Q000032:analysis; D015996:Survival Rate; D013997:Time Factors; D047368:Tumor Burden; D055815:Young Adult
chemical_list: C476213:ANO1 protein, human; D000075369:Anoctamin-1; D014408:Biomarkers, Tumor; D018118:Chloride Channels; D009363:Neoplasm Proteins; D013385:Succinate Dehydrogenase; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha