The pathologic evaluation of resected intestinal neoplasms plays an integral part in determining the patient’s prognosis and in selecting the appro-priate adjuvant therapy. As is true for other specimens, a systematic approach to your dissection is the best way to ensure that all of the appropriate information is included in your final report.
Start with the patient’s history. This should include both the patient’s clinical history (Crohn’s disease, ulcerative colitis, polyps, family history) and the relevant endoscopic findings. Next, iden-tify the segment of bowel that was resected, and orient the specimen. As described earily, the large intestine is readily distinguished from the small intestine by its larger diameter and the presence of longitudinal muscle bands (the teniae coli), sacculations (the haustra), and the ap-pendices epiploicae. In addition, the small intes-tine shows mucosal folds that stretch across the entire circumference of the bowel, whereas the large intestinal mucosal folds are discontinuous. The rectum can be distinguished from the colon by the absence of a peritoneal surface covering the rectum. Record the length and the diameter of the bowel. The diameter should be recorded both proximal and distal to any lesions. Look for and document the presence and appearance of any other structures, such as the appendix. Next, describe the serosa. Are any diverticula, gross perforations, or serosal nodules present?
As noted above, the rectum lacks a serosal lining. Therefore, the outer surface of the rectum represents a true soft tissue margin, and these soft tissues should be inked. Otherwise, only the proximal and distal margins need to be inked. When opening the bowel, make every effort not to cut through the tumor. First, localize the tumor by palpating the specimen and probing the lumen of the bowel with your finger, then open the bowel on the side opposite the tumor. If a tumor cannot be appreciated grossly, simply open the small intestine adjacent to the mesenvery, the colon along the anterior (free) teniae, and the rectum along the midline anteriorly. Once the specimen has been opened, gently rinse off the intestinal contents using a stream of isotonic saline.
Next, systematically describe the opened speci-men. Start with the tumor. Document its location relative to the margins and to any landmarks, such as the ileocecal valve or the pectinate line.
Describe the size of the tumor in its longitudinal and transverse dimensions, as well at its gross configuration (endophytic, pedunculated, sessile, diffusely infiltrative, or annular). It is especially critical to document tumor size for anal carcino-mas, since it is tumor size rather than depth of invasion that serves as the key feature for as-sessing ‘‘T’’ when staging the tumor. Multiple cancers should be looked for, described, and labeled separately. After the tumor has been described, make multiple parallel 2- to 3-mm sec-tions through the tumor, and note its deepest gross penetration. It is also important to note if bowel perforation (a hole in the bowel wall) is associated with the tumor. Also note the distance from the tumor to the soft tissue or radial margin. This is the distance from the outermost part of the tumor to the lateral margin of resection along a radius drawn from the center of the lumen of the bowel through the deepest penetration of the tumor. The soft tissue margin is only important for rectal cancers and for colon cancers located on the mesenteric aspect of the bowel.
After the tumor has been described, turn your attention to the remainder of the bowel. Be sys-tematic in your description. For example, begin with the mucosa, wall, and serosa of the proximal portion of the specimen and then proceed dis-tally. When describing the mucosa, note diverti-cula, changes of inflammatory bowel disease, polyps, and ischemic changes. A systematic ap-proach to your gross dictation will ensure that all important findings are included.
We like to examine the soft tissues for lymph nodes in the fresh state because the nodes are easier to palpate and because they retain their pink color, which contrasts to the yellow fat. The next step, therefore, is to dissect the mesentery. Look for and sample any lymph nodes adjacent to the point of ligation of the vascular pedicle, and designate these as the highest lymph nodes. Next, cut the mesentery close to the bowel, main-taining anatomic orientation. Do not remove any areas in which the tumor directly extends into the mesenteric fat. Sample these as a part of the deep margin after the specimen has been fixed. Then divide the detached mesenteric fat into groups: those proximal to the tumor, those at the level of the tumor, and those distal to the tumor. If any great vessels are present, identify and sepa-rately designate the nodes adjacent to them. Thinly section the mesenteric fat at each level, and examine and palpate each section for lymph nodes. Submit for histology each identified node. When looking for the nodes, remember that they are frequently present at the junction of the bowel wall and the mesentery. When submitting the lymph nodes for histologic processing, remember to designate the level from which they were taken. Also examine the veins and arteries in the mesentery for thrombi. If any are present, submit a representative section of the involved vessel for histologic examination. After the mesentery has been examined, separately bundle each level for fixation and storage. Should you ever have to return to the mesentery, the orientation will be preserved. The specimen can now be pinned to a wax tablet and fixed overnight.
After the specimen is well fixed, it can be sampled. Start with the tumor. Submit at least two sections: one from the edge of the tumor to show the junction of tumor and normal bowel, and one from the point of deepest tumor penetration into the wall of the bowel. If the tumor does not grossly appear to involve the bowel wall, then submit the entire base of the lesion to demonstrate the presence or absence of invasion.
Submit the proximal and distal margins. If the tumor is close to a margin, these sections should be perpendicular (longitudinal), and if the tumor is far from a margin, these sections can be parallel (transverse). Next, sample any other lesions.
When sampling polyps, remember to include both the head and stalk in your sections. Submit representative sections of normal bowel mucosa and wall, and submit representative sections of all remaining structures/organs, such as the appendix and terminal ileum. Remember that longitudinal sections are better than transverse sections when sampling the colon wall.
· What procedure was performed, and what structures/organs are present?
· What is the location of the tumor?
· What are the dimensions of the tumor?
· What is the gross configuration of the tumor (endophytic, pedunculated, sessile, diffusely infiltrating, annular)?
· What are the histologic type and grade of the neoplasm?
· What is the maximum depth of invasion of the tumor? Is it in situ (high-grade dysplasia), or does it extend into the lamina propria, sub-mucosa, muscularis propria, or through the muscularis propria into subserosa? Does the tumor extend into other organs, or does it ex-tend into the visceral peritoneum?
· Is there bowel wall perforation?
· Is any vascular invasion identified?
· What is the status of the margins (proximal, distal, and radial)?
· How many lymph node metastases were identified, and how many lymph nodes were sampled at each level?
· Are there mesenteric deposits? For staging purposes, tumor nodules in the pericolorectal fat without histologic evidence of residual lymph node are classified as regional node metastases
· if they have the form and smooth contour of a lymph node. Nodules with irregular contours are believed to reflect microscopic venous invasion using AJCC criteria.
· Are any other lesions noted (e.g., adenomas, intestinal inflammatory disease, dysplasia)?