Classification and Histological Characteristics of Colorectal Cancer

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Figure 1.
The large intestine (colon and rectum). The colon is divided anatomically into ascending, transverse, descending, and sigmoid sections. The sigmoid colon terminates in the rectum, which exits the body at the anus. Right-sided colorectal cancers (RCRCs) involve the ascending and transverse colon (left of dotted line); left-sided colorectal cancers (LCRCs) involve the descending and sigmoid colon as well as the rectum.

Table 1.

Basic characteristics of benign colorectal polyps

Benign Colorectal Polyps
Basic Shapes
Pedunculated—broad body with a narrow stalk, most common		Sessile—raised body, no stalk, difficult to locate
Common Types With Description
		Subtypes of adenomatous polyps
Adenomatous	Increased likelihood of cancer progression	Tubular—small, pedunculated; with tube-shaped crypts on microscopic exam Villous—large, sessile, elongated villi (velvety appearance) Tubulovillous—differing morphologies in different parts of the polyp
Hyperplastic	Overgrowth of cells; low chance of cancer progression
Inflammatory	Associated with inflammatory response (ulcerative colitis, Crohn’s disease)
Harmartomatous	Overgrowth of normal-appearing tissue; hereditary association (Peutz-Jeghers)
Sessile serrated	Histologically similar to hyperplastic; increased risk of malignant transformation

Table 2.

Colorectal cancer subtypes

Colorectal Cancers
Types	Adenocarcinoma—90% of all colorectal cancer types Adenosquamous carcinoma Spindle cell carcinoma Squamous cell carcinoma Undifferentiated carcinoma
Subtypes of adenocarcinoma	Cribriform-comedo Medullary Micropapillary Mucinous Serrated Signet ring