|Path Labs||CTools||Lab Instructors||ImageScope||Histology Normals||Histology Site||M1 Histopathology|
GI Path Lab 3: Part I
Reading Assignments (Robbins: Pathologic Basis of Disease, 8th Ed.)
**If there are conflicts with the lecture material, believe the lecture stuff!**
|815 - 821||Polyps and polyposis syndromes|
|821 - 826||Carcinoma of the colorectum|
|787 - 789||Carcinoid tumors|
Areas of Concentration
Upon completion of this exercise, you should be able to:
Colonic Adenomas in Familial Adenomatous Polyposis (FAP) and Colonic Carcinoma
In both of these slides, there is neoplastic epithelium that lines tubular structures. First, check the normal crypt epithelium to see what it looks like. It has many goblet cells alternating with squeezed columnar cells, and the nuclei of both cell types are small, uniform, and located at the base of the cells. In contrast, the neoplastic epithelium is different. In Slide 90, from a patient with familial adenomatous polyposis, there are many adenomas of different sizes within the mucosa. In the adenomas, the epithelium tends to be more uniform than in the carcinoma, but both types of epithelium have neoplastic (dysplastic) features. The nuclei are crowded, hyperchromatic, stratified, and take up a greater portion of the cell than they do in normal colonic epithelium. Since there is plenty of normal mucosa for comparison, these differences should be readily apparent. Notice also that the adenomatous epithelium tends to be located near the mucosal surface, with much less adenomatous epithelium appearing toward the base of the mucosa. Most of the adenomatous epithelial cells are tall columnar cells with no obvious differentiation, although there are also scattered dysplastic goblet cells and Paneth cells. The adenomatous tubules are generally uniform. In contrast, the carcinomatous epithelium lines tubules, but make little attempt at uniformity. There is greater stratification of their nuclei, mitotic figures are found readily, and in some places, clusters and strands of undifferentiated epithelial cells invade the stroma. These two slides, therefore, offer excellent comparisons between what pathologists refer to as adenomatous or benign neoplastic or low-grade dysplastic epithelium and carcinomatous or malignant neoplastic or highest grade dysplastic epithelium. It is epithelium of the type in Slide 90 that is considered to be the precursor of the epithelium in Slide 91. In fact, if you carefully examine Slide 91, you will find areas in which the epithelium begins to look more and more like that in Slide 90 with more uniform tubules, less nuclear stratification, and even a few goblet cells. Some adenomas are composed of one or two tubules lined by dysplastic epithelium that closely caricatures normal crypt epithelium. See if you can find them.
Metastatic Colorectal Carcinoma in Liver
In this slide of liver, there are several separate masses of carcinoma.
Small Intestine: Carcinoid Tumor
This is a typical gastrointestinal tract tumor of endocrine cells composed of nests and cords of uniform cells that look like they could have come from the islets of Langerhans or the pituitary or the parathyroid. They extend from the base of the mucosa through the wall into the mesenteric adipose tissue. These nests are surrounded by very dense collagenized (desmoplastic) stroma that is most impressive in the mesentery. Notice that the bowel is kinked at this point, as a result of the desmoplasia. The most common site of such gastrointestinal endocrine tumors is the appendix where they are usually incidental findings and do not cause any trouble. In the small intestine, the second most common site, they are likely to grow larger, produce symptoms, and even metastasize.
The answers to the path lab questions will be posted approximately 48-72 hours after the lab sessions. These are abbreviated answers, not a full discussion of the topics. You can find them in the M2 CTools site resources. In the folder for each sequence the will be a folder called 'Path Lab Resources'