Molecular testing of gastrointestinal tumours

Cancers of the gastrointestinal tract are a major cause of morbidity and mortality globally, and not surprisingly, there has been intense interest in identifying prognostic and predictive markers for new targeted therapies. The cancers of the gastrointestinal tract are unique in exemplifying in microcosm the axioms of molecular pathology: that amongst the various organs of the gastrointestinal tract, different molecular markers have different implications; that of the innumerable molecular alterations identified in these cancers, only an extremely small minority have proven clinical relevance; and perhaps most importantly, that molecular pathology practitioners must be prudent in maximising the use of small tissue samples to garner clinically important information. Here, we review the clinically-validated molecular targets in carcinomas of the oesophagus, stomach, colorectum and anal canal, and in gastrointestinal stromal tumours, and discuss a handful of markers which are likely to be of use in the future.