The volcano sign and mucus outflow by colonoscopy - Low grade appendiceal mucinous neoplasm

Colonoscopy. Volcano sign. Low grade appendiceal mucinous neoplasm. Conflict of interest: the authors declare no conflict of interest. Dear Editor, An 82-year-old female presented to a clinic with painless hematochezia. Her medical history was unremarkable and was referred to our hospital for further examination. Physical examination revealed was unremarkable and laboratory tests were normal. Colonoscopy revealed a submucosal tumor-like mass approximately 15 mm in size in the cecum. The appendiceal orifice was identified in the center of the prominence, showing the volcano sign (Fig. 1A and B). The yellowish mucus was discharged from the orifice like a lava flow, the so-called mucus outflow, when palpated with the biopsy forceps (Fig. 1C). As the abdominal computed tomography (CT) scan showed no abnormal findings suggestive of appendiceal enlargement, distant metastasis, or intra- abdominal tumor, she underwent laparoscopic appendectomy based on the diagnosis of appendiceal mucinous neoplasm. The pathological diagnosis was low grade appendiceal mucinous neoplasm (LAMN) without destructive invasion (Fig. 1D-F). The patient has not suffered recurrence or peritoneal pseudomyxoma for five years after surgery.

LAMN is a clinical entity characterized by the absence of infiltrative growth or destructive invasion but recognized as a borderline malignant tumor because it has a propensity for peritoneal dissemination, resulting in peritoneal pseudomyxoma (1). There are two types of LAMN: type I, in which mucus or endothelial cells remain in the appendiceal lumen, and type II, in which there is a high risk of deep submucosal invasion and transformation to peritoneal pseudomyxoma (1,2). The present case corresponded to type I. The differential diagnosis includes appendiceal polyps, lipomas, neuroendocrine neoplasms, and endometriosis (2,3), none of which are associated with the mucous outflow from the appendiceal orifice. There were also no findings suggestive of lipoma or neuroendocrine neoplasia on CT scan. Pathognomonic features of the mucus outflow may be helpful in differentiating these tumors (3,4), as shown here. Treatment is generally surgical resection, but there are no clear criteria regarding the surgical technique, and appendectomy or partial cecal resection is considered to be sufficient in cases of probable adenoma (1,2,5). In conclusion, our case underscores the importance of the volcano sign and the mucus outflow in the preoperative diagnosis of appendiceal mucinous neoplasm.

1. Umetsu SE, Kakar S. Staging of appendiceal mucinous neoplasms: challenges and recent updates. Hum Pathol 2023;132:65-76. DOI: 10.1016/j.humpath.2022.07.004 2. Shaib WL, Assi R, Shamseddine A, et al. Appendiceal mucinous neoplasms: diagnosis and management. Oncologist 2017;22:1107-16. DOI: 10.1634/theoncologist.2017-0081 3. Hamilton DL, Stormont JM. The volcano sign of appendiceal mucocele. Gastrointest Endosc 1989;35:453-6. DOI: 10.1016/s0016-5107(89)72860-1 4. Vashistha N, Deo A, Singhal D. Gastrointestinal: mucocele appendix with atypical “volcano sign”. J Gastroenterol Hepatol 2022;37:45. DOI: 10.1111/jgh.15541 5. Assarzadegan N, Montgomery E. What is new in the 2019 World Health Organization (WHO) classification of tumors of the digestive system: review of selected updates on neuroendocrine neoplasms, appendiceal tumors, and molecular testing. Arch Pathol Lab Med 2021;145:664-77. DOI: 10.5858/arpa.2019-0665-RA . Fig. 1. A. The appendiceal orifice was identified in the center of the prominence, showing the volcano sign. B. The volcano sign appeared clearly with indigo carmine dye. C. The yellowish mucus was discharged from the orifice like a lava flow, the so- called mucus outflow, when palpated with the biopsy forceps. D. The resected appendix was filled with viscous fluid. The mucinous lesion was located in the proximal lumen (arrow) of the vertical incised appendix. E. The mucosa was replaced by mucinous undulating epithelial proliferation (H&E ×12.5). F. Higher-power view shows the epithelium lined by tall columnar cells and cytoplasmic mucin vacuoles compressing the nucleus, making the diagnosis of low grade appendiceal mucinous neoplasm (H&E ×100).