6. Endocytoscopy

Fig. 6.1

Appearance of an endocytoscope (CF-H290ECI)

6.1.2 Diagnostic Performance of Colorectal Submucosal Cancers Using Endocytoscopes

Over ten clinical studies including one prospective trial [4] and one randomized trial [3] were conducted to clarify the potential of EC in diagnosis of colorectal lesions. In evaluating colorectal lesions by EC, the EC classification (Fig. 6.2) [4] for the staining mode and the EC-V classification (Fig. 6.3) [1] for the NBI mode are encouraged to be used (please see Sects. 6.1.2.1 and 6.1.2.2 for details). According to these trials, EC provided additional diagnostic values to conventional magnifying endoscopy in predicting the histology of T1b cancers; EC showed 95.7% accuracy with the NBI mode [1] and 96.3% accuracy with the staining mode [2] in diagnosis of these types of lesions. Therefore, EC has a potential of providing higher diagnostic performance in identification of T1b cancers than the previously available modalities such as magnified endoscopy.

../images/461529_1_En_6_Chapter/461529_1_En_6_Fig2_HTML.png — Fig. 6.2

EC classification

../images/461529_1_En_6_Chapter/461529_1_En_6_Fig3_HTML.jpg — Fig. 6.3

EC-V classification

6.1.2.1 EC Classification (Fig. 6.2)

EC classification was developed to support endoscopists in interpreting endocytoscopic images with the stained mode precisely. In determining the classification, we also referred to histopathological tissue diagnoses: structural atypia and cellular atypia. Thus, “endocytoscopic classification” was defined as focusing on the morphology of lumens and the shape of nuclei in endocytoscopic images. Nonneoplastic lesions were classified as EC1a and EC1b while neoplastic lesions as EC2, EC3a, and EC3b.

Details of the classification are as follows: Images showing roundish lumens and a regular pattern of uniformly sized fusiform nuclei were classified as EC1a, which corresponds to normal colorectal mucosa. Images showing narrow, serrated lumens and a dense pattern of small roundish nuclei were classified as EC1b, corresponding to hyperplastic polyps. Images showing neoplastic characteristics that correspond to histopathological tissue images ranging from low- to high-grade adenomas were classified as EC2. This was recognized by slit-like smooth lumens and a regular pattern of fusiform or roundish nuclei. Irregular and rough lumens and a large number of roundish nuclei strongly stained with methylene blue were classified as EC3a, corresponding to high-grade adenomas or slightly invasive submucosal cancers (T1a). Finally, images showing unclear gland formation and agglomeration of distorted nuclei strongly stained with methylene blue were classified as EC3b. In this group, the lumens were often difficult to recognize. The majority of EC3b tumors that exhibited such characteristics were actually T1b cancers or worse. All normal mucosae were classified as EC1a and all hyperplastic polyps as EC1b. According to a prospective study investigating a total of 213 colorectal lesions, adenomas were mainly classified as EC2, while T1b cancers or worse, which have the possibility of metastasis, were mainly EC3b. Assuming that an EC1b classification was diagnostic of hyperplastic polyps, we were able to differentiate nonneoplastic from neoplastic lesions with a sensitivity of 100% and a specificity of 100% (P < 0.05). Assuming that an EC3b classification was diagnostic of T1b cancers or worse, we were able to differentiate “T1b cancers or worse” from other neoplastic lesions (adenomas and T1a cancers) with a sensitivity of 90.1% and a specificity of 99.2% (P < 0.05) [4].

6.1.2.2 EC-V Classification (Fig. 6.3)

EC-C classification was developed to support endoscopists interpret endoscytoscopic images with the NBI mode precisely. We divided the EC-V pattern into three groups: EC-V1, EC-V2, and EC-V3. The ultra-magnified microvessels of the hyperplastic polyps were very fine and obscure (EC-V1 pattern). The microvessels of tubular adenomas were more clearly seen and showed a regular vessel network (EC-V2 pattern). The microvessels of invasive cancers were irregular (EC-V3 pattern); our definition of an irregular microvessel was one with an unusually large caliber and a tortuous course or a single vessel with an irregular vessel wall margin or caliber. The sensitivity, specificity, and accuracy of the EC-V1 pattern for diagnosing hyperplastic polyps were 95.5%, 99.4%, and 99.0%, respectively. The sensitivity, specificity, and accuracy of the EC-V3 pattern for diagnosing invasive cancer were 74.6%, 97.2%, and 88.6%, respectively. The diagnostic accuracy of the EC-V pattern for predicting hyperplastic polyps was comparable to the other modalities. According to our previously conducted retrospective analysis, for predicting invasive cancer, the EC with the NBI mode provides comparable diagnostic accuracy to narrowband imaging and pit pattern, although EC with the stained mode was slightly more accurate [1].

6.1.2.3 Case Presentation

Examples of the EC images were shown in Fig. 6.4a–c. This lesion is a T1b cancer whose diameter is 10 mm (Fig. 6.4a). EC images reveal the thick irregular vessels with the NBI mode (Fig. 6.4b) and the large distorted nuclei with unclear cellular lumens in the staining image (Fig. 6.4c). These EC findings are characteristics of T1b cancers, thus EC findings help endoscopists to diagnose this lesion as a T1b cancer with high confidence despite its small size. According to the EC and EC-V classification, Fig. 6.4b corresponds to EC3b, while Fig. 6.4c corresponds to EC-V3.