What Is the JNET Classification for Polyps?

The JNET classification is a diagnostic tool for visually categorizing colorectal polyps, which are growths on the lining of the colon or rectum. Developed by the Japan NBI Expert Team, the system helps endoscopists predict a polyp’s nature during a colonoscopy. By examining a polyp’s surface features and blood vessels, doctors can assess whether it is benign, precancerous, or potentially cancerous. This real-time evaluation helps determine the most appropriate action, from simple removal to more complex procedures, and standardizes communication among providers.

Defining JNET Classification

The JNET classification was established to differentiate between polyp types based on visual characteristics that correlate with their underlying histology. This allows for a non-invasive prediction of whether a polyp is a harmless hyperplastic type, a precancerous adenoma, or an invasive cancer.

By analyzing vessel patterns and mucosal surface texture, the system provides a structured framework to determine malignancy potential. The classification’s development was an improvement on previous systems, offering a more nuanced breakdown of polyp features to help guide immediate management strategies during an examination.

Advanced Endoscopic Imaging for JNET

The JNET classification relies on advanced imaging to enhance visualization of the colon’s inner lining. A primary technology is Narrow Band Imaging (NBI), which uses light filters to accentuate blood vessels and the mucosal surface. NBI filters light to specific wavelengths absorbed by hemoglobin, making surface capillaries appear brown and deeper vessels cyan. This contrast makes the vessel architecture clearer than under standard white light.

This enhanced view is combined with magnifying endoscopy, a technique that zooms in on the polyp’s surface up to 100 times. This magnification reveals microscopic details of the surface and vessel patterns needed to apply the JNET classification accurately.

Without these technologies, the details required for the classification would be invisible. The adoption of high-definition endoscopes with NBI and magnification has been necessary for the JNET system’s clinical use.

Understanding JNET Polyp Types

The JNET classification system has four main categories, each defined by vessel and surface patterns seen with NBI and magnification. This categorization allows for a precise prediction of a polyp’s histology.

• Type 1 polyps have surface vessels that are not visible or are similar to the surrounding mucosa. Their surface pattern has regular dark or white spots, indicating hyperplastic polyps or sessile serrated lesions with low cancer risk.
• Type 2A polyps display regular and uniform vessel patterns, often in a reticular or spiral arrangement. The surface pattern is also regular, suggesting low-grade adenomas, which are precancerous but slow-growing.
• Type 2B polyps exhibit irregular vessel patterns with varying sizes and shapes, and the surface pattern is also irregular. These traits suggest a high-grade adenoma or a shallow submucosal invasive cancer.
• Type 3 polyps are identified by highly irregular or disrupted vessel patterns and an amorphous surface. These features indicate a deep submucosal invasive cancer that has grown into deeper layers of the colon wall.

Clinical Applications of JNET

The JNET classification directly influences how polyps are managed during a colonoscopy, allowing endoscopists to make immediate treatment decisions. This “optical biopsy” capability streamlines the process from diagnosis to treatment. For instance, a JNET Type 1 polyp is likely benign and may be removed without pathological analysis, a practice known as “resect and discard.”

A Type 2A polyp, identified as a low-grade adenoma, can be removed using standard techniques like endoscopic mucosal resection (EMR). The identification of a JNET Type 2B or Type 3 polyp signals a more serious finding. A Type 2B lesion may require a specialized technique like endoscopic submucosal dissection (ESD) for complete removal.

For a Type 3 polyp, suspected to be a deep invasive cancer, the patient might be referred for surgical resection. This system helps avoid unnecessary procedures for benign lesions while ensuring that potentially malignant polyps receive timely intervention.