Colon
Carcinoma
Posttreatment changes


Topic Completed: 4 February 2021

Minor changes: 4 February 2021

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PubMed Search: Posttreatment "rectal carcinoma"

Raul S. Gonzalez, M.D.
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Cite this page: Gonzalez RS. Posttreatment changes. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumorposttreatment.html. Accessed April 18th, 2021.
Essential features
  • 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
Sites
  • Rectum only; neoadjuvant treatment is generally not given for colonic carcinoma
Clinical features
  • Treatment often shrinks tumors, reducing risk of local recurrence
  • Patients may experience treatment related complications or anorectal dysfunction (Dis Colon Rectum 2011;54:901)
Gross description
  • 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

Contributed by Raul S. Gonzalez, M.D.

Posttreatment changes of rectal carcinoma

Positive stains
  • 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?

  1. Appendix
  2. Ascending colon
  3. Transverse colon
  4. Rectum
Board review style answer #1
D. Rectum

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