Goblet cell adenocarcinoma of the appendix

Goblet cell adenocarcinoma is an amphicrine tumour: its cells contain both mucin, like intestinal goblet cells, and neuroendocrine granules, and it grows in a concentric, infiltrative pattern through the appendiceal wall, often without a visible mass, so it is usually discovered after appendicectomy for appendicitis. Because of its neuroendocrine component it was long called goblet cell carcinoid and lumped with appendiceal neuroendocrine tumours, but it spreads like a carcinoma, to the peritoneum and, in women, to the ovaries, and does not express somatostatin receptors or respond to somatostatin analogues. The 2019 WHO classification renamed it goblet cell adenocarcinoma and grades it by the proportion of tubular or clustered goblet cell growth against poorly cohesive or signet ring growth (grades 1 to 3), replacing the earlier Tang classification; grade and stage determine survival, which is long for grade 1 tumours confined to the appendix and short for grade 3 tumours with peritoneal spread. The genetics are distinct from both appendiceal adenocarcinoma and neuroendocrine tumours, with mutations in chromatin-remodelling and Wnt pathway genes and few KRAS mutations.

Right hemicolectomy with lymphadenectomy is recommended for almost all patients because nodal spread is common even with small tumours, and bilateral oophorectomy is considered in postmenopausal women. Adjuvant chemotherapy with FOLFOX or CAPOX is used for node-positive or grade 2 to 3 disease by analogy with colon cancer, and peritoneal metastases are treated with cytoreductive surgery and HIPEC in selected patients, with outcomes between those of low-grade pseudomyxoma peritonei and signet ring cell carcinoma. Metastatic disease receives colorectal chemotherapy regimens; platinum-etoposide, the treatment for neuroendocrine carcinoma, is not appropriate. Because the disease is so rare, care is best delivered in a peritoneal surface oncology centre with pathology review.