Adenocarcinoma of the Appendix
Definition
- Malignant gland forming appendiceal neoplasm
Note:
- We reserve the term "adenocarcinoma" for neoplasms characterized by invasive glands and or signet ring cells
- Neoplasms characterized by dissecting mucin (with or without cells), but not invasive glands behave differently and are classified separately as
(see Differential Diagnosis at left or follow the links below)
- Mucinous neoplasm with low risk of recurrence
- Mucinous neoplasm with high risk of recurrence
- WHO classifies both of these as low grade mucinous neoplasm
Diagnostic Criteria
- All types are quite rare
- All show overtly malignant features
- Invasion of appendiceal wall by neoplastic epithelium
- Jagged neoplastic glands beyond the muscularis mucosa
- Usually exhibits high grade cytologic atypia
- Frequent mitotic figures
- Usually exhibits architectural complexity and/or discohesive infiltration
- Peritoneal implants typically invasive
- Frequent metastasis to nodes, liver
- Mucinous adenocarcinoma is similar to that of the colorectum
- High grade cytology within mucin pools or direct mural invasion by neoplastic glands
- Must be >50% mucin
- Very rarely associated with clinical pseudomyxoma peritonei
- Most peritoneal involvement by carcinoma is better characterized as peritoneal carcinomatosis
- Intestinal type adenocarcinoma shows features of usual colorectal adenocarcinoma
- Signet ring carcinoma is similar to that of the colorectum
- >50% must be made up of signet ring cells
- Frequent metastasis to ovary
- Very poor prognosis
- Distinguish from carcinoma ex-goblet cell carcinoid
- Lacks any typical goblet cell carcinoid pattern in the primary tumor
- Appendiceal adenocarcinomas have been reported associated with serrated polyps
- The nature and extent of association is not clear
- Virtually all appendiceal adenocarcinomas of all types are microsatellite stable
- Poor prognosis for all types
- <10% 10 year survival
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates : 10/7/10, 11/21/11, 2/10/12
