The gallbladder and extrahepatic bile ducts show a limited spectrum of inflammatory and neoplastic disorders, but these disorders are significant because they affect a large proportion of the world’s population. The most common (>95%) is cholelithiasis. Inflammation in the gallbladder…
Anal Anatomic and Histologic Landmarks The anal canal encompasses the distal most 3 to 4 cm of the most distal intestinal tract. It is defined proximally by the palpable upper border of the internal sphincter muscle, which is a continuation…
Molecular testing of colorectal carcinomaAlthough there are numerous esoteric tests that a molecular pathology laboratory may use on colorectal cancer (CRC) specimens, there are two tests that are the most common and important—assessment of mismatch repair (MMR) integrity and RAS/RAF…
A large variety of neoplasms may occur in the colorectum, reflecting the complexity of this organ and its cellular components. This chapter focuses primarily on those neoplasms arising from the epithelial and neuroendocrine cells of the colorectum. Epithelial neoplasms that…
Nearly every histologic type of polyp involving the gastrointestinal (GI) tract can occur in a sporadic or syndromic setting. In general, a syndromic diagnosis must be suspected when multiple polyps type are present concurrently or sequentially on surveillance colonoscopy; when…
Mucosal biopsies from the colon are obtained most commonly (1) in acutely symptomatic patients with the possibility of an ischemic, infectious, or drug-induced colitis; (2) when graft-versus-host disease (GVHD) needs to be ruled out; or (3) in those with chronic…
Surgical pathologists who evaluate specimens from the gastrointestinal (GI) tract for possible infections must first attempt to differentiate histologic changes suggesting infection from other inflammatory processes. After this determination, dedicated attempts must be made to diagnose the specific infectious organisms.…
Congenital and Acquired Anatomic Anomalies of the Appendix Abnormal Location, Size, and Absence of the Appendix The appendix can have a host of anatomic abnormalities, including atypical location, duplication, and congenital absence. The position of appendix is determined by the…
Gastrointestinal Stromal Tumor Gastrointestinal stromal tumors (GISTs) are the most common soft tissue tumors of the gastrointestinal (GI) tract, with a worldwide annual incidence of about 15 cases per million. Although there was historic controversy over the distinction between GIST,…
The small intestine represents 75% of the length and 90% of the surface area of the gastrointestinal (GI) tract, yet neoplasms of the small intestine are rare, accounting for only 1% to 2% of all GI neoplasms and fewer than…