Microscopic description:

Solid tumor cell clusters, crypt-like structures or tubules of mucus-secreting cells distended with mucin resembling goblet cells or signet ring cells, but also with eosinophilic cytoplasm resembling classic carcinoid in some cells

Nuclei are bland and monomorphic

Also called mucinous carcinoid, adenocarcinoid, microglandular goblet cell carcinoma, crypt cell carcinoma

Shows divergent differentiation of normal crypt stem cells (columnar, endocrine, goblet cell, Paneth cell lineages) between typical carcinoma and adenocarcinoma

Less common than classic carcinoids (6% of all appendiceal carcinoids)

Usually in older patients

Up to 20% spread beyond appendix; often to ovaries or peritoneal surfaces

Metastases may have goblet cell carcinoid, signet ring cell carcinoma or classical carcinoid histology

Discussion:

Poor prognostic factors: solid pattern or carcinomatous pattern in 50%+ of tumor; also perineural invasion, lymphatic invasion, spread beyond appendix, serosal involvement at presentation, incomplete excision at appendix base

Grossly, thickened appendiceal wall, usually no gross tumor

Usually spares mucosa and infiltrates muscularis propria and periappendiceal fat

Cell clusters, crypt-like structures or tubules of mucus-secreting cells distended with mucin resembling goblet cells or signet ring cells, but also with eosinophilic cytoplasm resembling classic carcinoid in some cells

Extensive perineural invasion common

May have pools of extracellular mucin

Positive stains: Mucin (mucicarmine, PAS, PAS diastase, Alcian blue), CEA, cytokeratin (especially CK20), lysozyme, chromogranin A, serotonin, synaptophysin (usually)

Differential diagnosis:

  • Metastatic signet ring cell carcinoma: infiltrative, signet ring cells
  • Classic carcinoid tumor: no goblet cell differentiation, no intracellular mucus vacuoles, no Paneth cell differentiation
  • Mucinous adenocarcinoma: more aggressive, irregular fused structures without distinct lumina

References:

Chetty R, Klimstra DS, Henson DE, Albores-Saavedra J. Combined classical carcinoid and goblet cell carcinoid tumor: a new morphologic variant of carcinoid tumor of the appendix. Am J Surg Pathol. 2010 Aug;34(8):1163-7. doi: 10.1097/PAS.0b013e3181e52916. PMID: 20631606.

Roy P, Chetty R. Goblet cell carcinoid tumors of the appendix: An overview. World J Gastrointest Oncol. 2010 Jun 15;2(6):251-8. doi: 10.4251/wjgo.v2.i6.251. PMID: 21160637; PMCID: PMC2998842.

Chen V, Qizilbash AH. Goblet cell carcinoid tumor of the appendix. Report of five cases and review of the literature. Arch Pathol Lab Med. 1979 Apr;103(4):180-2. PMID: 218519.

CASE IMAGES