The Importance of the Macroscopic Classification of Colorectal Neoplasms

The importance and prevalence of the superficial lesions in the colon and rectum caught worldwide public attention in 2008 when Soetikno and colleagues reported the prevalence of non-polypoid (flat and depressed) colorectal neoplasms in asymptomatic and symptomatic adults in North America and the public media disseminated their findings. The publication put to rest the question of whether or not the flat and depressed colorectal neoplasms exist in Western countries; flat and depressed colorectal neoplasms can be found throughout the world. In this article, the author highlights the importance of the macroscopic classification of the colorectal neoplasm and emphasizes the distinction between so-called flat lesions (IIa and IIb) and 0-IIc (superficial depressed) neoplastic colorectal lesions.

In Japan, neoplastic lesions of the stomach that have a superficial endoscopic appearance (the lesion appears resectable by endoscopy) are classified as a subtype called “type 0.” This term was chosen to distinguish the classification of superficial lesions from Borrmann’s classification, proposed in 1926, which described only advanced gastric cancers. This classification method of superficial gastric neoplasia was later applied to the colon and rectum.

The development of the classification of superficial, shallow, depressed-type neoplastic lesions, now classified as 0-IIc, has followed a similar path to that of gastric and early esophageal cancers, but with significant delay. Kariya reported the first 0-IIc lesions in 1977, but until 1993 when Kudo reported the 0-IIc-carcinoma cohort and classification, type 0-IIc carcinomas were thought to be a uniquely Japanese phenomenon. The macroscopic classification of colorectal neoplasms, as defined by the Japanese Society for Cancer of the Colon and Rectum, is shown in Box 1 . It is essentially identical to that of the gastric superficial neoplasms, with the exception that it does not have type 0-III (the excavated type) because this type does not exist in the colon and rectum.

Box 1

Type 0: Superficial tumors
- Type 0-I: Protruded type
  - 0-Ip: Pedunculated
  - 0-Isp: Sub-pedunculated
  - 0-Is: Sessile
- Type 0-II: Superficial type
  - 0-IIa: Superficial elevated
  - 0-IIb: Flat type
  - 0-IIc: Superficial depressed type
Type 1 to 5: Masses with m. propria involvement

Macroscopic types of primary tumors of the colon and rectum

In 1998, the author’s colleagues, Fujii and colleagues, demonstrated the existence and prevalence of 0-IIa and 0-IIc lesions outside Japan in an English population. Saitoh and colleagues and Teixera subsequently reported the incidence of these lesions in a North American and South American population, respectively. By 2003, the importance of the superficial neoplastic lesions in the esophagus, stomach, and colon began to be recognized in Western countries. The development of the Paris classification is important because it provides recognition of the potential importance of type 0-IIa and 0-IIc and it provides a method for standard classification throughout the world.

The importance and prevalence of the superficial lesions in the colon and rectum caught worldwide public attention in 2008 when Soetikno and colleagues reported the prevalence of non-polypoid (flat and depressed) colorectal neoplasms (NP-CRNs) in asymptomatic and symptomatic adults in North America. The publication put to rest the question of whether or not the flat and depressed colorectal neoplasms exist in Western countries; flat and depressed colorectal neoplasms can be found throughout the world. In this article, the author highlights the importance of the macroscopic classification of the colorectal neoplasm and emphasizes the distinction between so-called flat lesions (IIa and IIb) and superficial depressed (0-IIc) neoplastic colorectal lesions.

Basic principles

Endoscopic Classification of Superficial Neoplastic Lesions

The Paris endoscopic classification of superficial neoplastic lesions of the digestive tract established a consensus criterion for macroscopic classification of superficial 0-I polypoid and 0-II flat, elevated, and depressed neoplasia. In the colon and rectum, the Paris classification focuses on the degree of protrusion of the lesion, comparing the height of the lesion with that of the closed cups of biopsy forceps (2.5 mm). Lesions protruding above the level of the closed jaws of the biopsy forceps are classified as Is (sessile) lesions; those that are below this level are classified as 0-IIa (elevated); and those at the same level as the forceps (completely flat) are classified as 0-IIb (flat). Regarding depressed lesions, the entire thickness of the neoplasia is located below the level of normal mucosa, resulting in a well-defined, depressed area (0-IIc) ( Figs. 1–3 ). A subgroup of superficially elevated lesions (0-IIa) may reach a large lateral diameter (>10 mm) without much increase in height; in the colon, these lesions are called laterally spreading tumors (LST) ( Fig. 4 ). In the experiences of the National Cancer Center Hospital, Japan, type 0-IIa comprises nearly half of all type 0 lesions, whereas type 0-IIc, including the combined type, comprises approximately 2%. However, completely flat lesions (0-IIb) are extremely infrequent in contrast with those in the stomach or esophagus ( Fig. 5 ).