Colon

Carcinoma

Adenocarcinoma

Author: Raul S. Gonzalez, M.D.

Editorial Board Member: Catherine E. Hagen, M.D.

Topic Completed: 10 May 2021

Minor changes: 10 May 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: Adenocarcinoma[TI] colon[TI] review[PT]

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Table of Contents

Cite this page: Gonzalez RS. Adenocarcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumoradenocarcinoma.html. Accessed October 21st, 2021.

Definition / general

Glandular neoplasm of the colorectum, representing 98% of colonic cancers (therefore, most details in the general colon carcinoma section pertain to adenocarcinomas)
9 WHO recognized subtypes: adenoma-like, adenosquamous, carcinoma with sarcomatoid components, medullary, micropapillary, mucinous, serrated, signet ring cell, undifferentiated
Uncommon subtypes are clear cell adenocarcinoma, low grade tubuloglandular adenocarcinoma and villous / adenoma-like adenocarcinoma (Am J Surg Pathol 2006;30:1022, Histopathology 2016;68:183)

Essential features

Most common primary colon carcinoma
Typically arises through chromosomal instability pathway (70 - 80%) or microsatellite instability pathway (10 - 15%)
Stage is most important prognostic factor

Clinical features

Increased carcinoma risk in patients with polyposis syndromes, Lynch syndrome and inflammatory bowel disease
Right sided tumors cause anemia, weakness and fatigue
Left sided tumors cause change in bowel habits (diarrhea or constipation)
Superficial tumors only rarely cause lymph node metastases due to distribution of lymphatics in colon

Diagnosis

Generally discovered on colonoscopy and confirmed on biopsy

Prognostic factors

Good prognostic factors:
- Microsatellite instability (Medicine (Baltimore) 2018;97:e0019)
- Increased tumor infiltrating lymphocytes (Am J Surg Pathol 2020;44:536)
Poor prognostic factors:
- Advanced stage, higher grade, lymphovascular and perineural invasion (Surg Pathol Clin 2020;13:503)
- Positive margins
- High tumor budding (Mod Pathol 2012;25:1315)
- CDX2 loss (World J Gastroenterol 2015;21:1457)
- High stromal content (Histopathology 2018;73:197)

Case reports

29 year old man with colonic adenocarcinoma metastasizing as a germ cell neoplasm (Arch Pathol Lab Med 2001;125:558)

Treatment

Surgical resection is generally required unless tumor is small and confined to a polyp
Adjuvant therapy given for patients with lymph node metastases
Neoadjuvant therapy often given for rectal carcinomas

Gross description

Usually single, polypoid or ulcerated mass
May cause serosal puckering if muscularis propria is involved
Right colon tumors tend to be polypoid and exophytic, while left colon tumors tend to be annular, encircling lesions

Gross images

Images hosted on other servers:

Early, flat tumor

Flat, small adenocarcinoma

Invasive mucinous adenocarcinoma

Exophytic lesion

Microscopic (histologic) description

Usually well or moderately differentiated gland forming carcinoma with marked desmoplasia, particularly at edge of tumor
Glands often cribriform and filled with necrotic debris (dirty necrosis), in both primary and metastatic sites
Inflammatory cells and scattered neuroendocrine cells are common (Pol J Pathol 2005;56:89)
Intramural venous invasion may be easier to identify using an elastin stain (J Clin Pathol 2002;55:17)
Well differentiated:
- 15 - 20% of all carcinomas
- Well formed glands or simple tubules with uniform, basally oriented nuclei
- Somewhat resembles adenomatous epithelium
Moderately differentiated:
- 60 - 70% of all carcinomas
- Tubules may be simple, complex or slightly irregular
- Nuclear polarity lost
Poorly differentiated:
- 15 - 20% all of carcinomas
- Less than 50% gland formation
- Majority of tumor (excluding advancing edge) consists of sheets of cells without gland formation
- Usually right sided (Hepatogastroenterology 2004;51:1698)
Note: preoperative histologic grading is not accurate (J Med Assoc Thai 2005;88:1535)

Microscopic (histologic) images

Contributed by Raul S. Gonzalez, M.D.

Low power

High power

Dirty necrosis

Cribriforming

Desmoplasia

Lymphovascular invasion

Contributed by Semir Vranic, M.D., Ph.D. and Beverly Wang, M.D.

Poorly differentiated adenocarcinoma

Adenocarcinoma

Images hosted on other servers:

Whole mount scan

Moderately differentiated

Dirty necrosis in gland lumens

Venous invasion

Serosal penetration

Detached carcinoma cells

Signet ring morphology

Lymph node metastasis

Positive stains

CK20 (Mod Pathol 2000;13:962)
CDX2 (superior to villin: Am J Surg Pathol 2003;27:303)
Also: AMACR (Am J Surg Pathol 2002;26:926)
Sometimes estrogen receptor (Hum Pathol 2001;32:940)
CD10 in stromal cells (Hum Pathol 2002;33:806)
SATB2

Negative stains

CK7, except in rectal adenocarcinomas (Appl Immunohistochem Mol Morphol 2009;17:196)

Molecular / cytogenetics description

Most commonly mutated genes include APC, TP53 and KRAS
Molecular classification of carcinomas has been proposed (Histopathology 2007;50:113)
Tumors can be screened for microsatellite instability via immunohistochemistry for MLH1, MSH2, MSH6 and PMS2

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