Small bowel, Gastrointestinal stromal tumour

This specimen photograph shows a segment of resected small bowel with a round well-circumscribed mesenteric nodule. On cross-section, the mass appears well-demarcated, fleshy, with possible hemorrhage and small areas of cystic degeneration. These findings have been described in some gastrointestinal stromal tumours (GISTs) harbouring platelet-derived growth factor receptor α (PDGFRα) gene mutations. Other molecular alterations encountered in GIST include mutations in KIT (most common), BRAF, RAS, NF1, and SDH deficiency. GIST represents the most common mesenchymal tumour of the gastrointestinal tract and is thought to arise from the interstitial cells of Cajal. Accurate diagnosis is important as some GISTs are amenable to targeted therapy.