PATHOLOGY TEACH AND TELL: PEDIATRIC GASTROINTESTINAL STROMAL TUMOR

A14-year-old boy, with no signi¢cant past medical or family history, presented with a 3-month history of vomiting and epigastric discomfort. There was no dysphagia or hematemesis and no systemic symptoms were present. Review of systems was otherwise unremarkable. On physical exmination, he was a well-nourished adolescent with no stigmata of chronic disease but a ¢rm mass was palpable in the epigastrium. Gastroscopic examination demonstrated macroscopically normal mucosa overlying a smooth polypoid lesion with associated gastric wall distortion by a mass arising from the posterior stomach wall. Computerized tomography con¢rmed the presence of a soft tissue mass within the posterior inferior aspect of the gastric wall, which also appeared to extend into the surrounding transverse mesocolon. Modi¢ed partial gastrectomy was carried out that revealed an umbilicated polypoid nodule arising from the posterior gastric wall, 4 cm in maximum extent, with numerous further nodules present extending into the transverse mesocolon. Several nodules were adherent to transverse colon, a portion of which had been resected (Figure 1). The nodules showed a homogeneous soft, cream-yellow cut-surface throughout. The gastric mucosa was macroscopically unremarkable. Histological sections demonstrated a tumor, apparently originating within the muscularis propria of the stomach, composedpredominantly of interlacing fascicles of plump spindle cells with minimal cellular pleomorphism (Figure 2).The overlyingmucosawas not ulceratedbut showedmoderate nonspeci¢c gastritis.The tumor cells show strong positive immunostaining for CD117 in a membranous pattern (Figure 3) and also were focally positive for CD34.Tumor cells did not express desmin, smooth muscle actin, or S100 protein.

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