Tumors of the colon and rectum can either be benign (non-cancerous) or malignant (cancerous). There are certain tumors that are classified as atypical (uncertain or unspecified behavior) meaning that some behave in a benign manner, or some behave in a malignant manner. A majority of the colorectal tumors diagnosed via lab studies (biopsy) are benign.

The World Health Organization (WHO) is an authoritative body that compiles, prepares, and publishes histological and molecular classification of tumors, via their Blue Books, based on research inputs from experts worldwide. These reference books chiefly aid in global cancer research, provide gold standards for tumor diagnosis, and help in treating cancer patients.

According to the WHO Classification of Digestive System Tumors (2019), 5th Ed., Vol. 1, benign and malignant tumors of the colon and rectum are classified in the following manner:

Tumors of the colon and rectum:

Epithelial tumors

• Benign epithelial tumors and precursors
  • Colorectal serrated lesions and polyps
  • Conventional colorectal adenoma
  • Inflammatory bowel disease-associated dysplasia of the colorectum
• Malignant epithelial tumors
  • Colorectal adenocarcinoma: It constitutes between 90-98% of all colorectal cancers and is the most common type noted. The malignancy is generally seen in middle-aged and older adults over 40 years of age
  • Colorectal neuroendocrine neoplasms: These are described as malignant epithelial cancers of the large intestine/colon and rectum. These tumors are usually observed in middle-aged and older adults

Additional colon and rectal tumor articles (on DoveMed) that are not part of WHO Classification of Digestive System Tumors:

Adenoma-like Adenocarcinoma of Colon and Rectum: It is a very rare subtype of colorectal adenocarcinoma. It is generally seen in middle-aged and older adults over 40 years of age.

Adenosquamous Carcinoma of Colon and Rectum: It is a rare histological subtype of colorectal adenocarcinoma having malignant squamous cells and malignant glandular cells. It is generally seen in middle-aged and older adults over 40 years of age.

Angiomyolipoma of Colon: It is a very uncommon extrarenal angiomyolipoma that may be present in the colon. Almost all the cases have been reported in adult men. An angiomyolipoma is a benign tumor that is a mixture of blood vessels, smooth muscles, and fat.

Colon Cancer: It is a malignant tumor of the colon and rectum observed in adult males and females worldwide. Since Rectal Cancer shares many similar features with Colon Cancer, they are typically grouped together and known as Colorectal Cancer.

Colon Polyps: These are benign tumors that occur from abnormal cell growth within the colonic tissue. These tumors are generally noted in older adults.

Colonic Arteriovenous Malformation: It is a benign condition that may have a congenital origin. The symptoms due to the malformation may occur at any age in one’s life.

Colorectal Carcinoma with Sarcomatoid Component: It is a very rare and aggressive histological subtype of colorectal adenocarcinoma. Middle-aged and older adults may be affected by this tumor.

Colorectal Mixed Neuroendocrine-Non-Neuroendocrine Neoplasms (MiNENs): These are subtypes of colorectal neuroendocrine neoplasms (NENs), which are described as malignant epithelial cancers of the colon and rectum. These tumors are usually observed in middle-aged and older adults.

Colorectal Neuroendocrine Carcinomas (NECs): These are subtypes of colorectal neuroendocrine neoplasms (NENs), which are described as malignant epithelial cancers of the colon and rectum. These tumors are usually observed in middle-aged and older adults.

Colorectal Neuroendocrine Tumors: These are subtypes of colorectal neuroendocrine neoplasms (NENs), which are described as malignant epithelial cancers of the colon and rectum. These tumors are usually observed in middle-aged and older adults.

Cribriform Comedo-type Adenocarcinoma of Colon and Rectum: It is a rare histological subtype of colorectal adenocarcinoma. It is generally seen in middle-aged and older adults over 40 years of age.

Diffuse Large B-Cell Lymphoma (DLBCL) of Colon and Rectum: It is a rare, B-cell non-Hodgkin’s lymphoma that affects older men and women. It is the most common subtype of colorectal lymphoma.

Ganglioneuroma of Colon: It is a rare, benign lesion that forms in the colon. It usually arises in older adults (men and women).

Granular Cell Tumor (GCT) of Colon: It is a rare, benign lesion that forms in the colon. It can occur in middle-aged and older men and women.

Hyperplastic Polyps of the Colon: These are benign lesions that form in the colon. These are usually observed in older adults.

Inflammatory Fibroid Polyp (IFP) of Colon: It is a rare, benign lesion that forms in the colon. The tumor usually arises in older adults.

Inflammatory Myofibroblastic Tumor of Colon: It is a very rare, mostly benign tumor of the colon. It can grow to large sizes and is generally seen in younger populations.

Leiomyoma of Colon: It is a rare, benign lesion that forms in the colon. The tumor usually arises in older adults.

Low-Grade Tubuloglandular Adenocarcinoma (LGTGA) of Colon and Rectum: It is a very rare subtype of colorectal adenocarcinoma. It is generally seen in middle-aged and older adults over 40 years of age.

Lymphoma of Colon and Rectum: It is an uncommon lymphoma of the gastrointestinal tract that is generally observed in elderly men and women.

MALT Lymphoma of Colon: It is a rare non-gastric type of extranodal marginal zone lymphoma affecting the colon in older adults. The condition is also known as Marginal Zone Lymphoma of Colon. 

Medullary Adenocarcinoma of Colon and Rectum: It is a rare histological subtype of colorectal adenocarcinoma that is usually observed in middle-aged and older adults.

Medullary Carcinoma of Colon and Rectum: It is a rare histological subtype of colorectal adenocarcinoma, typically observed in adults over the age of 70 years.

Micropapillary Adenocarcinoma of Colon and Rectum: It is a rare histological variant of colorectal adenocarcinoma. It is generally seen in middle-aged and older adults over 40 years of age.

Mucinous Adenocarcinoma (MAC) of Colon and Rectum: It is a histological subtype of colorectal adenocarcinoma. It is generally seen in middle-aged and older adults over 40 years of age.

Perineurioma of Colon: It is a rare, benign lesion that forms in the colon. It usually arises in older adults.

Poorly-Cohesive Carcinoma of Colon and Rectum: It is an extremely rare histological subtype of colorectal adenocarcinoma that typically affects older adults.

Primary Clear Cell Adenocarcinoma of Colon and Rectum: It is a very rare subtype of colorectal adenocarcinoma that shows a preference for elderly adult males.

Schwann Cell Hamartoma of Colon: It is a rare, benign, non-cancerous lesion that forms in the colon. It usually arises in older adults.

Serrated Adenocarcinoma (SAC) of Colon and Rectum: It is a rare histological subtype of colorectal adenocarcinoma. It is generally seen in middle-aged and older adults over 40 years of age.

Sessile Serrated Polyps (SSPs) of the Colon: These are benign tumors that can develop into colorectal cancers if left untreated. These tumors are usually observed in older adults.

Signet Ring-Cell Carcinoma (SRCC) of Colon and Rectum: It is a rare histological subtype of colorectal adenocarcinoma. It is generally seen in adults around 40 years of age.

Spindle Cell Carcinoma of Colon and Rectum: It is a histological subtype of colorectal adenocarcinoma. It is generally seen in middle-aged and older adults over 40 years of age.

Tubular Adenoma of the Colon: It is a type of adenoma (tumor) in the large intestine. Tubular adenomas are considered “pre-malignant” tumors and develop in middle-age to elderly adults.

Undifferentiated Carcinoma of Colon and Rectum: It is a rare histological variant of colorectal adenocarcinoma. It is generally seen in middle-aged and older adults over 40 years of age.