7 - Gastrointestinal Tract

Abstract

Cytologic sampling of the upper luminal gastrointestinal (GI) tract has long been used for the detection of malignant and premalignant lesions and infections. Direct visualization of the mucosa, coupled with ultrasound imaging of submucosal structures, allows for the collection of mucosal brushings, submucosal fine-needle aspirates (FNA), and mucosal biopsy specimens, all with a single procedure. Ultrasound-guided endoscopic FNA permits the needle to reach even deeper lesions, including those that are extrinsic to the GI tract but impinging on the lumen, like a metastatic malignancy for staging purposes. The introduction of nonendoscopic sampling has made cytologic evaluation of the esophagus suitable for screening for high-risk populations in a primary care setting. This chapter introduces commonly encountered entities in the GI tract with a brief description of epidemiology followed by detailed discussion of morphology, with exemplary illustrations and differential diagnosis. The value and appropriate use of ancillary studies is examined and applied to the differential diagnosis. A section is devoted to the anal Pap test, including its efficacy and benefits in screening high-risk populations.