" XXXX in adults: distinctive histology predicts genotype and clinical behavior.

@entity1 @entity675 @entity39 @entity5 @entity1711 @entity9387 @entity1710 @entity3 @entity674 @entity2280 @entity2213
@entity674 ( @entity674 ) rarely affect @entity1 , mainly @entity1 . Pediatric @entity674 typically arise in the stomach as @entity5 with a multinodular growth pattern, epithelioid morphology, lymph node @entity3 , an absence of KIT and @entity675 gene mutations, and indolent behavior. Occasional @entity674 in adults show similar features. Such @entity5 are not widely recognized. @entity674 with a multinodular growth pattern in @entity1 over the age of 18 years were retrieved from surgical and consultation files. @entity1710 and @entity1711 -stained slides were reviewed, immunohistochemistry was performed, and KIT (exons 9, 11, 13, and 17) and @entity675 (exons 12, 14, and 18) genes were screened for mutations. Clinical follow-up was obtained. Sixteen cases were identified, affecting 13 @entity1 and 3 @entity1 (median age, 31.5 y; range, 19 to 56 y), all in the stomach. The mean @entity5 size was 5.4 cm (range, 1.8 to 11 cm); 4 were multifocal. All @entity5 showed a multinodular or plexiform architecture and epithelioid (N=3) or mixed epithelioid and spindle cell (N=13) morphology. Five @entity5 had vascular invasion; 6 had focal @entity39 . Mitotic activity ranged from 3 to 156/50 high-power fields (8 @entity5 had  <=5/50 high-power fields). Using Armed Forces Institute of Pathology risk stratification, categories for @entity5 were: none (N=2), very low risk (N=3), low risk (N=3), moderate risk (N=3), and high risk (N=5). By immunohistochemistry, all @entity5 were positive for KIT, 82% @entity9387 , 72% @entity2280 , 18% caldesmon, 9% S-100, 8% smooth muscle actin, and 0% desmin. All @entity5 were wild type for KIT and @entity675 in the exons that were screened. At primary resection, 9 @entity1 (56%) had lymph node @entity3 and 3 @entity1 had liver @entity3 . Follow-up ranged from 16 months to 16 years (median, 5 y). Two @entity5 recurred locally in the stomach and 7 @entity1 developed subsequent @entity3 to the lymph nodes (N=5), liver (N=3), and peritoneum/omentum (N=3). @entity5 from 7 @entity1 with @entity3 were Armed Forces Institute of Pathology low risk, very low risk, or no risk of recurrence. None of the @entity3 responded to treatment with @entity2213 . One @entity1 died of disseminated liver and intra-abdominal @entity3 and the remaining @entity1 were alive at last follow-up. Gastric @entity674 in adults with a multinodular or plexiform growth pattern and epithelioid or mixed morphology are similar to pediatric @entity674 . Unlike conventional adult @entity674 , this distinctive subset predominantly affects @entity1 , often metastasizes to lymph nodes, and lacks mutations in KIT and @entity675 . Current risk assessment criteria do not reliably predict behavior for this group. Although @entity3 are common and most @entity5 are @entity2213 resistant, they pursue a relatively indolent clinical course. Recognition of "pediatric-type" @entity674 in adults is critical for prognosis, appropriate therapy, and follow-up.
