Pai et al proposed a classification for mucinous neoplasms of the appendix. The correct classification of an appendiceal mucinous neoplasm is essential for optimum management. The authors are from Stanford University.
Parameters:
(1) cytologic grade
(2) extra-appendiceal mucin
(3) extra-appendiceal epithelial cells
(4) invasion (irregular, jagged neoplastic glands beyond the muscularis mucosa)
Cytologic Grade
Extra-
Appendiceal Mucin
Extra-
Appendiceal
Epithelium
Invasion
Diagnosis
low grade
absent
absent
absent
mucinous adenoma
low grade
present, acellular
absent
absent
low-grade mucinous neoplasm, low risk to recur
low grade
present
present
absent
low-grade mucinous neoplasm, high risk to recur
often high grade
NA
NA
present
mucinous adeno-
carcinoma
A low-grade mucinous epithelium was composed of columnar cells with a flattened or villous architecture.
The diagnosis of mucinous adenoma without risk of recurrence would be applied to a mucinous adenoma that has been completely excised with a negative surgical margin. Any residual disease would be associated with a risk of recurrence.
A high-grade cytology without invasion through the muscularis mucosa would indicate a mucinous adenocarcinoma in situ.
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