Colon tumor
Carcinoma
Post-treatment changes of rectal carcinoma

Author: Raul Gonzalez M.D. (see Authors page)

Revised: 16 December 2015, last major update December 2015

Copyright: (c) 2002-2015, PathologyOutlines.com, Inc.

PubMed Search: Post-treatment [title] rectal carcinoma
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)
Micro 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)
Micro Images
Images hosted on PathOut server:

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Images courtesy of Dr. Raul Gonzalez



Positive Stains
  • Cytokeratin may be used to detect rare residual tumor cells