Appendiceal mucinous neoplasm in an inverted appendix found on prior colonoscopy

Inverted appendix does not cause any symptoms but may cause differential diagnostic problems on colonoscopy. Other than resulting from surgery, an inverted appendix may represent acute appendicitis (Fig. 1A), tumors of the appendix (Fig. 2), mucocele (Fig. 3), fecalith (Fig. 1B and C), or worms Inverted appendix can also be a normal variant (Figure 4, Figure 5, Figure 6).

Figure 1.

A, Inverted appendix as acute appendicitis. B, Inverted appendix as a benign appendix with prominent fecalith. C, Inverted appendix as a benign appendix with prominent fecalith.

Figure 2.

Inverted appendix, neuroma.

Figure 3.

Inverted appendix before biopsy.

Figure 4.

Inverted appendix, normal variant.

Figure 5.

Inverted appendix, normal variant.

Figure 6.

Inverted appendix, normal variant.

Case Report

An asymptomatic 57-year-old man was referred to our institution for evaluation of a 1-cm nodule at the appendiceal orifice versus an inverted appendix. Prior surveillance colonoscopy 5 years earlier had revealed a normal appendiceal orifice. We performed a complete colonoscopy with intra-appendiceal mucosal biopsies (Video 1, available online at www.VideoGIE.org). Examination of biopsy specimens from the mucosa revealed a low-grade intraepithelial mucinous neoplasm (Figs. 7 and 8).

Figure 7.

Histologic slide from cold forceps biopsy (H&E, orig. mag. × 10).

Figure 8.

Surgical pathologic slide showing appendiceal neoplasia (H&E, orig. mag. × 10).

Linear EUS was successfully advanced to the cecum after pleating the colon. Linear EUS showed a distended appendix without periappendiceal lymphadenopathy or appendiceal mass.

Subsequent magnetic resonance imaging (MRI) of the abdomen showed a distended appendix without obvious invasion to the surrounding tissues (Fig. 9). The patient underwent appendectomy and partial cecectomy. Pathologic examination of the surgical specimen revealed a low-grade appendiceal mucinous neoplasm (Fig. 10). The margins were negative for neoplasia.

Figure 9.

Magnetic resonance image of the distended appendix measuring 1.77 cm × 1.43 cm.

Figure 10.

Surgical pathologic slide showing uninvolved cecal margin (H&E, orig. mag. × 15).

Conclusion

An inverted appendix should not be ignored because it may represent other pathologic changes. Cross-sectional imaging with either CT or MRI should be obtained. EUS can be helpful in evaluating this entity. In our case, analysis of biopsy specimens from the appendiceal lumen were decisive in identifying the histologic structure of an inverted appendix.

Disclosure

All authors disclosed no financial relationships relevant to this publication.

Supplementary data

Video

Uncommon presentation of inverted appendix-appendiceal mucinous neoplasm.