Appendiceal adenocarcinoma is a rare primary malignant epithelial tumor of the appendix, accounting for 10-20% of all appendiceal neoplasms. It shows histological and biological similarity to colorectal adenocarcinoma. Characterized on CT by irregular-margined, heterogeneously enhancing mass, appendiceal luminal destruction, periappendiceal invasion, and regional lymphadenopathy. Diagnosis is often delayed because clinical presentation mimics acute appendicitis.
Age Range
40-80
Peak Age
60
Gender
Male predominant
Prevalence
Rare
Appendiceal adenocarcinoma follows the same adenoma-carcinoma sequence as colorectal adenocarcinoma. Mucosal dysplasia → adenoma → invasive carcinoma progression develops over years. Molecular pathways such as APC, KRAS, TP53, and microsatellite instability are shared with colorectal cancer. The tumor usually begins at the appendiceal base or body, obstructing the lumen and causing secondary appendicitis. In advanced cases, serosal penetration can lead to peritoneal spread (carcinomatosis). The mucinous subtype (50-60%) produces abundant mucin creating low-density cystic/mucinous collections and may lead to pseudomyxoma peritonei if ruptured. The non-mucinous colonic subtype shows the same CT features as colorectal adenocarcinoma.
On CT, an irregular-margined, heterogeneously enhancing solid mass at the appendiceal base/body combined with cecal wall invasion and regional lymphadenopathy represents the diagnostic triad of appendiceal adenocarcinoma. This combination is critical for differentiation from acute appendicitis, carcinoid, and GCC. In the mucinous subtype, low-density mucinous collections and mural nodularity are additional distinguishing findings.
An irregular-margined, heterogeneously enhancing solid mass is seen at the appendiceal base or body. The mass typically measures 2-5 cm showing exophytic or endophytic growth from the appendiceal wall. Necrosis areas show low density while solid component shows moderate-to-marked enhancement.
Report Sentence
An irregular-margined, heterogeneously enhancing solid mass measuring ... x ... cm at the appendiceal base/body is noted; primary appendiceal malignancy should be considered.
Direct tumor invasion into the cecal wall appears on CT as cecal pole thickening, irregular contour, and loss of normal fat plane. In advanced cases, invasion into the terminal ileum or adjacent bowel loops may also accompany.
Report Sentence
The mass invades the cecal pole wall with loss of normal fat plane and wall irregularity.
Regional lymphadenopathy (ileocolic, right colic, mesenteric LAP) indicates metastatic spread of adenocarcinoma. Lymph nodes may show short axis >1 cm, round morphology, heterogeneous enhancement, or necrosis.
Report Sentence
Pathological lymph nodes with ... mm short axis in the ileocolic/right colic region are noted, consistent with metastatic lymphadenopathy.
In the mucinous adenocarcinoma subtype, low-density mucinous collections may be seen within or around the mass. The appendiceal lumen may be dilated with mucin creating a 'mucocele'-like appearance. Mucinous implants on peritoneal surfaces may lead to pseudomyxoma peritonei.
Report Sentence
Mucinous collection and mural nodularity in the appendiceal lumen are noted; mucinous adenocarcinoma should be considered.
In advanced adenocarcinoma, enhancing nodular implants on peritoneal surfaces, omental caking, and ascites may be seen. In mucinous subtype, low-density mucinous ascites and gelatinous peritoneal implants (pseudomyxoma peritonei) are seen.
Report Sentence
Enhancing implants on peritoneal surfaces and ascites are noted, consistent with peritoneal carcinomatosis.
On MRI, adenocarcinoma shows heterogeneous signal intensity on T2-weighted sequences. Solid component shows intermediate signal, necrotic areas high signal, fibrosis low signal. Mucinous component is very bright on T2. Marked diffusion restriction on DWI supports malignancy.
Report Sentence
The mass in the appendix shows heterogeneous signal on MRI with diffusion restriction on DWI, consistent with malignancy.
Criteria
More than 50% of tumor volume contains extracellular mucin pools; cystic/mucinous component dominant
Distinct Features
CT shows low-density mucinous collections (10-30 HU), mural nodularity, mucocele-like appearance. High risk of pseudomyxoma peritonei. Prognosis worse than non-mucinous type.
Criteria
Histologically identical to colorectal adenocarcinoma; minimal or no mucin production
Distinct Features
CT shows dominant solid mass without mucinous collection. Staged and treated like colorectal cancer. Surgery: right hemicolectomy + lymphadenectomy.
Distinguishing Feature
Carcinoid forms well-defined, homogeneously enhancing small nodule usually at tip; adenocarcinoma is irregular-margined, heterogeneous, larger, and usually at base
Distinguishing Feature
GCC shows concentric diffuse wall thickening without forming focal mass; adenocarcinoma has distinct focal mass and luminal destruction
Distinguishing Feature
Appendiceal abscess shows rim-enhancing fluid collection without solid mass component; adenocarcinoma has dominant solid heterogeneous mass without collection (unless perforated)
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
3-monthAppendiceal adenocarcinoma is staged and treated like colorectal cancer. Standard surgery is right hemicolectomy + ileocolic lymphadenectomy. Adjuvant chemotherapy (5-FU/oxaliplatin-based — FOLFOX) is applied in stage III-IV disease. In mucinous adenocarcinoma with peritoneal spread, HIPEC + cytoreductive surgery should be evaluated. Multidisciplinary approach is required in pseudomyxoma peritonei. Follow-up: CT every 3-6 months for first 2 years, CEA monitoring. 5-year survival: stage I 90%, stage II 65-70%, stage III 30-40%, stage IV 10-15%. Colonoscopy should be performed to exclude synchronous colorectal cancer.
Treatment of appendiceal adenocarcinoma is right hemicolectomy (simple appendectomy is insufficient). Mucinous subtype has high risk of developing peritoneal pseudomyxoma peritonei (PMP) requiring cytoreductive surgery + HIPEC. Staging follows colorectal cancer TNM system. 5-year survival is 60-70% in localized disease, 20-30% in advanced stage. Chemotherapy regimens used in colorectal cancer (FOLFOX/FOLFIRI) are applied.