ASCRS Ch33 - Appendiceal Neoplasms

Chapter 33, "Appendiceal Neoplasms," ASCRS Textbook of Colon and Rectal Surgery, 4th edition. Authors: Tan SA, Stocchi L. Book pp. 577–586 (References end p.586).

Textbook reference chapter (not primary literature). Covers the appendiceal-mass differential and three broad tumor categories: epithelial neoplasms (adenocarcinoma; other mucinous lesions per the PSOGI classification), and neuroendocrine tumors of the appendix (aNEN). Substantially corroborates the wiki's existing Appendiceal Neoplasms page (previously sourced from Hoehn 2021 - Appendiceal Neoplasms, a primary-literature review) with largely consistent staging and management framework; contributes some additional PSOGI-classification granularity (HAMN, serrated polyp, simple mucocele as distinct entities; the colonoscopic "volcano sign"), NCDB-sourced adjuvant-chemotherapy utilization data for adenocarcinoma, explicit surveillance-interval detail, and appendiceal-NET-specific staging (AJCC TNM Table 33.1) and mesoappendix-invasion risk detail not previously captured on the wiki.

Adenocarcinoma

• Differential diagnosis of an appendiceal mass on presentation: appendicitis/periappendiceal abscess, mucocele, epithelial neoplasm (adenocarcinoma or mucinous neoplasm), NET, and — rarely — cecal cancer involving the appendiceal base.
• Histologic subtypes mirror colorectal adenocarcinoma (mucinous, signet-ring, colonic-type); staged using the same AJCC TNM framework as colorectal cancer, with the appendix-specific Tis(LAMN) and M1a/M1b/M1c modifiers.
• Extent of resection: right hemicolectomy is recommended for invasive adenocarcinoma given the meaningful nodal-metastasis risk even in small tumors; appendectomy alone is reserved for very select low-risk, completely-excised low-grade disease. This corroborates the existing page's colonic-type-adenocarcinoma management recommendation.
• Perforated tumors: perforation at presentation (or intraoperatively) changes staging (M1) and management — these patients require the same completion oncologic resection plus a broader workup for peritoneal spread, and are counseled regarding a meaningfully worse prognosis than nonperforated disease.
• Adjuvant therapy: National Cancer Database (NCDB) data show adjuvant chemotherapy utilization patterns for appendiceal adenocarcinoma broadly follow colon-cancer practice (i.e., offered for stage III and high-risk stage II disease), though the evidence base is smaller and extrapolated from colorectal-cancer trials rather than appendix-specific RCTs — no appendix-specific adjuvant regimen exists.
• Surveillance: post-treatment surveillance intervals mirror colorectal cancer surveillance (physical exam, CEA, CT imaging, colonoscopy on a similar schedule) — see Colorectal Cancer Surveillance After Curative Treatment for the detailed interval schedule; the chapter does not describe an appendix-specific surveillance protocol distinct from that framework.

Other mucinous lesions (PSOGI classification)

• Full PSOGI spectrum from benign to malignant: serrated polyp (hyperplastic-type epithelial change, no mucin accumulation) → simple/retention mucocele (mucus-filled appendix from luminal obstruction, no epithelial neoplasia) → LAMN (low-grade cytology, no infiltrative invasion) → HAMN (high-grade cytologic atypia but — unlike mucinous adenocarcinoma — still no infiltrative invasion; a hybrid category between LAMN and invasive mucinous adenocarcinoma) → mucinous adenocarcinoma (infiltrative invasion present). This confirms and extends the existing page's LAMN/HGAMN/adenocarcinoma framing with the two additional benign/borderline entities (serrated polyp, simple mucocele) and the HAMN category, which the existing page's classification list did not separately name.
• Colonoscopic "volcano sign": a mucin plug protruding from the appendiceal orifice, described as a characteristic (though not universal) endoscopic finding in mucinous appendiceal neoplasia — useful when colonoscopy is performed for another indication and incidentally identifies the lesion.
• Acellular vs. cellular peritoneal mucin distinction (already on the existing page: 4% vs. 40% progression-to-PMP risk) is corroborated, with added emphasis on surveillance-interval stratification by this same distinction — closer-interval imaging surveillance recommended for cellular mucin given the higher progression risk.
• "Preemptive" cytoreductive surgery/HIPEC: for higher-grade or cellular-mucin disease with significant PMP-progression risk, some centers advocate early (preemptive) CRS/HIPEC rather than watchful surveillance — framed as an evolving, center-dependent practice rather than a firm guideline recommendation.

Neuroendocrine tumors (aNEN)

• Epidemiology: incidence and distribution described by sex and age — aNEN incidence peaks earlier than most GI NETs (often diagnosed incidentally in younger patients, including a meaningful pediatric/young-adult fraction, given the disease's usual incidental discovery at appendectomy for presumed appendicitis).
• Clinical presentation: overwhelmingly incidental at appendectomy performed for another indication (i.e., presumed acute appendicitis) — corroborates the existing page's framing.
• Tumor size remains the single most reliable predictor of malignant/metastatic potential, corroborating the existing page's size-tiered LN-involvement data (15% ≤1cm, 47% 1–2cm, 86% >2cm).
• Mesoappendix invasion is highlighted as an additional adverse risk feature independent of size, not separately called out on the existing page — depth of mesoappendiceal invasion factors into the decision for completion right hemicolectomy alongside tumor size and base involvement.
• Ki-67 proliferative index used for grading per WHO criteria (as on the existing page); not separately quantified with new figures in this chapter.
• AJCC TNM staging (Table 33.1): appendiceal NETs are staged with an appendix-specific TNM schema distinct from other GI NETs (T-stage driven primarily by size and mesoappendiceal invasion depth) — the table is referenced here for completeness; full stage-by-stage TNM detail was not re-transcribed onto the wiki page given the existing page's already-thorough size/LN-risk framework covers the same clinical decision points.
• Right hemicolectomy indications: >2cm, base involvement, or mesoappendiceal invasion — corroborates and slightly extends the existing page's >2cm/base-involvement criteria with the mesoappendiceal-invasion addition above.
• Somatostatin analogues for advanced/metastatic disease and CgA-based surveillance post-resection are both mentioned consistent with general GI-NET practice (see Small Bowel Neuroendocrine Tumors (NETs) for the detailed primary-source trial data on SSAs) — no appendix-NET-specific trial data given.

Open items / gaps

• Table 33.1's full stage-by-stage TNM criteria were not individually transcribed onto the wiki (summarized narratively above) — refer back to this source chapter if exact T/N/M cutoffs are needed for a specific staging determination.
• No NCDB citation detail (patient count, exact utilization percentages) was captured with enough precision to state as a hard figure — captured only as a qualitative practice pattern above.