Table of ContentsEssential features | Sites | Clinical features | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Sample pathology report | Board review style question #1 | Board review style answer #1
Cite this page: Gonzalez RS. Posttreatment changes. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumorposttreatment.html. Accessed April 18th, 2021.
- Rectal tumors often receive neoadjuvant treatment before resection
- Microscopic findings include fibrosis and acellular mucin
- Acellular mucin does not equal viable residual tumor and serial sections to hunt for rare cancer cells are not warranted
- Rectum only; neoadjuvant treatment is generally not given for colonic carcinoma
- Treatment often shrinks tumors, reducing risk of local recurrence
- Patients may experience treatment related complications or anorectal dysfunction (Dis Colon Rectum 2011;54:901)
- Flat, firm mass with central ulceration
- May be no identifiable lesion
- Unless residual tumor is grossly obvious, entire lesion site should be submitted for examination
- Completeness of mesorectal excision should be assessed (J Clin Pathol 2007;60:849)
Microscopic (histologic) description
- Microscopic changes include fibrosis, acellular mucin, necrotic tumor, ulceration and hemosiderin
- Viable residual tumor may appear well, moderate or poorly differentiated
- Lymph node metastases may remain viable, even if entire primary tumor is destroyed; viable tumor deposits also may be seen and portend poor outcome (Mod Pathol 2014;27:1281)
- Various grading systems exist for tumor response, with poor concordance (Hum Pathol 2012;43:1917)
- Acellular mucin should not be interpreted as residual tumor (Am J Surg Pathol 2011;35:127)
- Deeper sections to search for rare residual tumor cells has little bearing on patient outcome (Histopathology 2011;59:650)
Microscopic (histologic) images
- Cytokeratins may be used to detect rare residual tumor cells
Sample pathology report
- Rectum, resection:
- Segment of rectum with prominent reactive change and fibrosis, consistent with therapy effect (see comment)
- Negative for residual malignancy.
- Margins of resection unremarkable.
- Comment: The entire grossly abnormal area was submitted for microscopic examination.
Board review style question #1
Neoadjuvant therapy is usually given for large intestine carcinomas in what location?
- Ascending colon
- Transverse colon