Colon (tumor & nontumor)
Carcinoma
Adenocarcinoma
Author: Raul S. Gonzalez, M.D.
Topic Completed: 1 November 2015
Minor changes: 30 July 2020
Copyright: 2002-2019, PathologyOutlines.com, Inc.
PubMed Search: Adenocarcinoma [title] colon
Table of Contents
Definition / general | Essential features | Clinical features | Diagnosis | Prognostic factors | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Molecular / cytogenetics description | Videos | Differential diagnosis | Additional referencesCite this page: Gonzalez R. Adenocarcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumoradenocarcinoma.html. Accessed August 7th, 2020.
Definition / general
- Glandular neoplasm of the colorectum, representing 98% of colonic cancers (therefore, most details in the general colon carcinoma section pertain to adenocarcinomas)
- Six WHO recognized subtypes: Cribriform-comedo, Medullary, Micropapillary, Mucinous, Serrated, Signet ring cell
- Uncommon subtypes are clear cell adenocarcinoma, low grade tubuloglandular adenocarcinoma (Am J Surg Pathol 2006;30:1022), and villous / adenoma-like adenocarcinoma (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
- Poor prognostic factors include advanced stage, higher grade and positive margins
- Tumor budding is linked to worse outcome (Mod Pathol 2012;25:1315)
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 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 Dr. Semir Vranic
Various images
Contributed by Dr. Beverly Wang
Various images
Images hosted on other servers:
Whole mount scan
Moderately differentiated
Mucinous and undifferentiated areas
"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)
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
Videos
Differential diagnosis
- Endometrioid adenocarcinoma arising in colonic endometriosis (Am J Surg Pathol 2000;24:513): PAX8 positive, CDX2 negative
Additional references
