Getting the GIST: a pictorial review of the various patterns of presentation of gastrointestinal stromal tumors on imaging. 
Gastrointestinal stromal tumors (GISTs), the most common mesenchymal tumors of the gastrointestinal tract, are a relatively recently described entity.  Most exhibit a mutated tyrosine kinase receptor gene and in some capacity are treated by tyrosine kinase inhibitors.  GISTs can occur across the age spectrum but are more common in patients older than 40 years.  They exhibit a wide range of clinical presentations and imaging characteristics.  All patterns of enhancement on contrast enhanced computed tomography (CECT) can be seen with GISTs, including hypoenhancing, isoenhancing, and hyperenhancing tumors.  They can be large or small, endoluminal or exophytic.  Clinical presentations include asymptomatic patients, nonspecific symptoms, obstruction, and bleeding.  Bleeding can take the form of slow, intraluminal GI bleeding or massive intraperitoneal bleeding secondary to rupture and can be seen regardless of the enhancement pattern.  Some can cavitate, ulcerate, rupture or cause fistulae.  The radiologist's knowledge of the variety of combinations of presentations can narrow the differential diagnosis and ultimately lead to faster diagnosis and treatment.