Appendiceal mucinous neoplasms are the second most common tumors after carcinoid tumors in all excised appendices [1]. Low-grade appendiceal mucinous neoplasms are often found incidentally (~50 %), first discovered on radiography, endoscopy, or during surgery [2]. On endoscopy, they often appear as submucosal tumor-like elevations at the appendicular orifice [3]; there are no reports of associated epithelial changes. Herein we report two cases of endoscopically observed epithelial changes in low-grade appendiceal mucinous neoplasms ([Video 1]).
Video 1 Low-grade appendiceal mucinous neoplasms observed on magnifying endoscopy.
Case 1: A 72-year-old woman underwent colonoscopy for contrast accumulation in the appendix on 18F-fluorodeoxyglucose positron emission tomography-computed tomography ([Fig. 1 a, b, c]). Colonoscopy revealed a slightly elevated whitish lesion covered with a mucus cap in the cecum at the appendiceal orifice ([Fig. 2 a, b]). Magnifying narrow-band imaging (NBI) showed no vessel pattern and regular, wavy, elongated surface structures ([Fig. 2 c]). Using chromoendoscopy with indigo carmine, the boundary of the lesion was clearly visualized ([Fig. 2 d]). Magnifying red dichromatic imaging with indigo carmine clearly showed regular, wavy, elongated, branched surface structures ([Fig. 2 e]). Magnifying chromoendoscopy using crystal violet showed a wavy, branched pit, although the staining was not as clear as with other methods, probably owing to adherent mucus ([Fig. 2 f]). Histopathological examination following ileocecal resection revealed a low-grade appendiceal mucinous neoplasm ([Fig. 3 a, b]).
Fig. 1 a, b
18F-fluorodeoxyglucose positron emission tomography-computed tomography showing accumulation of the radiotracer in the appendix (arrow). c Computed tomography showing no lesions.
Fig. 2 Endoscopic images showing a slightly elevated whitish lesion covered with a mucus cap in the cecum near the appendiceal orifice. a, b White light. c Magnifying narrow-band imaging. d Magnifying chromoendoscopy using indigo carmine. e Magnifying red dichromatic imaging with indigo carmine. fMagnifying chromoendoscopy using crystal violet staining.
Fig. 3 Histological examination (hematoxylin and eosin stained). a The distribution of lesions in the resection specimen is shown along with the boundary between normal mucosa and low-grade appendiceal mucinous neoplasm (the green line shows the area of low-grade appendiceal mucinous neoplasm with prominent mucous adhesion). b A magnified view of the area of low-grade appendiceal mucinous neoplasm; the mucinous epithelial cells are filiform with low-grade cytological atypia.
Case 2: A 74-year-old man underwent colonoscopy for appendiceal enlargement on computed tomography that showed a similar lesion as described in case 1 ([Fig. 4 a]). Magnifying NBI, chromoendoscopy with indigo carmine, and magnifying chromoendoscopy using crystal violet showed the same findings as in case 1 ([Fig. 4 b, c, d]). Following ileocecal resection, histopathology revealed a low-grade appendiceal mucinous neoplasm ([Fig. 5 a, b]) with some adenocarcinoma components in the tail of the appendix.
Fig. 4 Endoscopic images showing a slightly elevated whitish lesion covered with a mucus cap in the cecum near the appendiceal orifice. a White light. b Magnifying narrow-band imaging. c Magnifying chromoendoscopy using indigo carmine. d Magnifying chromoendoscopy using crystal violet staining.
Fig. 5 Histological examination (hematoxylin and eosin stained). a The distribution of lesions in the resection specimen is shown along with the boundary between the normal mucosa and low-grade appendiceal mucinous neoplasm (the green line shows the area of low-grade appendiceal mucinous neoplasm). b A magnified view of the area of low-grade appendiceal mucinous neoplasm; the mucinous epithelial cells are villous with low-grade cytological atypia.
In these cases, low-grade appendiceal mucinous neoplasms were observed as whitish, slightly elevated lesions covered with a mucus cap, and no blood vessels could be identified. The findings were more similar to serrated lesions than adenomas.
Endoscopy_UCTN_Code_CCL_1AD_2AB
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