Appendiceal mucinous neoplasm is a spectrum disease characterized by proliferation of mucin-producing neoplastic cells of the appendiceal mucosa. Classified as low-grade appendiceal mucinous neoplasm (LAMN), high-grade appendiceal mucinous neoplasm (HAMN), and mucinous adenocarcinoma. Calcified-wall dilated appendix (mucocele) on CT is characteristic. Most important complication is pseudomyxoma peritonei (PMP) after perforation — widespread mucinous material accumulation in peritoneal cavity.
Age Range
40-80
Peak Age
60
Gender
Female predominant
Prevalence
Rare
Appendiceal mucinous neoplasms begin with neoplastic transformation of mucosal epithelial cells — these cells produce and secrete excessive mucin. Mucin accumulation dilates the appendiceal lumen (mucocele). KRAS mutation (80%+) and GNAS mutation (50%+) are the most common genetic alterations. As the lumen dilates, the wall thins and peripheral calcification may develop — creating calcified-wall cystic dilation on CT. Capsule rupture (spontaneous or surgical) causes mucinous material spread into peritoneal cavity → pseudomyxoma peritonei (PMP). In PMP, mucinous material accumulates on omentum, peritoneal surfaces, and organs — described as 'jelly belly'. On CT, low-density (mucinous) peritoneal collections, scalloping (flattening/indentation on organ surfaces), and calcified peritoneal implants are seen.
Dilated appendix filled with low-density mucinous material surrounded by thin curvilinear peripheral calcification — signature finding of appendiceal mucinous neoplasm. This 'porcelain appendix' appearance distinguishes from acute appendicitis and is critically important for surgical planning (capsule rupture → PMP risk).
Dilated appendix (diameter >15 mm) with calcified wall. Lumen filled with low-density mucinous material (0-20 HU). Wall calcification thin, curvilinear, and peripheral.
Report Sentence
Calcified-wall dilation (mucocele) of the appendix with low-density intraluminal mucinous material is seen; appendiceal mucinous neoplasm should be considered.
Widespread low-density (mucinous) collections in peritoneal cavity, scalloping on organ surfaces (especially liver, spleen), and omental cake. Characteristic CT findings of PMP.
Report Sentence
Widespread low-density mucinous peritoneal collections, organ surface scalloping, and omental cake are seen, consistent with pseudomyxoma peritonei.
Thin curvilinear peripheral wall calcification — 'porcelain appendix' appearance. Best evaluated on non-contrast CT.
Report Sentence
Thin curvilinear peripheral calcification in the appendiceal wall is seen, favoring mucinous neoplasm.
Scalloping on organ surfaces in PMP — flattening/indentation on liver and spleen surfaces due to mucinous material pressure.
Report Sentence
Scalloping due to mucinous material is seen on liver and spleen surfaces.
Cystic dilated appendix on US — anechoic/hypoechoic mucinous content. Posterior acoustic shadowing may be seen due to wall calcification. Onion-skin sign (layered mucin) is specific finding.
Report Sentence
A cystic dilated appendix is seen in the right lower quadrant, suggesting mucinous neoplasm; further evaluation with CT is recommended.
Hyperintense mucinous content on T2W — water-like high signal in dilated appendix lumen. Low-intermediate signal on T1W (depending on mucin concentration).
Report Sentence
Hyperintense mucinous content on T2W is seen in the dilated appendix.
Criteria
Low-grade epithelial dysplasia. Push-type invasion (pushing margin). KRAS+GNAS mutation common.
Distinct Features
Well-defined mucocele on CT. Low but present PMP risk. Appendectomy sufficient (with complete resection). Maintaining intact capsule critical.
Criteria
High-grade epithelial dysplasia. No destructive invasion but dysplasia prominent.
Distinct Features
PMP risk higher than LAMN. Right hemicolectomy may be considered. Close follow-up needed.
Criteria
Destructive stromal invasion present. High risk of peritoneal spread (PMP).
Distinct Features
Irregular wall thickening, mural nodule, peritoneal implants on CT. Right hemicolectomy + CRS/HIPEC (cytoreductive surgery + hyperthermic intraperitoneal chemotherapy) standard treatment.
Distinguishing Feature
Acute appendicitis shows periappendiceal fat stranding, wall enhancement, and acute inflammatory findings. Mucinous neoplasm shows calcified wall, low-density mucinous content, and minimal/absent fat stranding.
Distinguishing Feature
Cecal adenocarcinoma shows solid mass formation, apple-core appearance, and lymphadenopathy. Mucinous neoplasm shows cystic mucocele formation and calcified wall.
Distinguishing Feature
Appendiceal carcinoid appears as small (<2 cm), solid, hypervascular nodule. Mucinous neoplasm shows cystic, low-density dilation.
Distinguishing Feature
Endometriosis is T1 hyperintense (hemorrhagic), T2 hypointense (fibrotic) solid nodule. Mucinous neoplasm shows cystic, T2 hyperintense (mucinous) dilation with calcified wall.
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
6-monthSurgical treatment is fundamental in appendiceal mucinous neoplasm. BIOPSY SHOULD NOT BE PERFORMED — percutaneous or endoscopic biopsy may cause capsule rupture and mucinous material spread to peritoneal cavity (PMP). Intact mucocele: laparoscopic appendectomy (preserving capsule integrity) or right hemicolectomy (large lesion or cecal base involved). If PMP developed: CRS (cytoreductive surgery — complete peritoneal surface clearance) + HIPEC (hyperthermic intraperitoneal chemotherapy — mitomycin C or oxaliplatin) is standard treatment. Follow-up: CT + tumor markers (CEA, CA19-9, CA-125) every 6 months. In PMP, 5-year survival 80-90% for LAMN-origin, 20-40% for adenocarcinoma-origin.
Requires surgical resection. Rupture must be avoided (pseudomyxoma peritonei risk). Low-grade mucinous neoplasm has good prognosis. HIPEC is considered in high-grade or pseudomyxoma cases.