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CLASSIFICATION
Classification
Appendiceal orifice lesion classification (Toyonaga type)
Superficial cecal lesions near the appendiceal orifice classified by contact and depth of extension into the appendix (Toyonaga classification). Guides ESD difficulty and en-bloc resection feasibility. Type 3a is deep invasion after appendectomy (Oung 2019).
Classification overview
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Type 0 · Proximal, not touching
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Type 1 · Touches orifice
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Type 2 · Partial invasion, edge visible
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Type 3 · Deep invasion, edge not seen
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After appendectomy
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Type 3a · Deep invasion after appendectomy
Type 0
Proximal, not touching
Relation
Proximity to the appendiceal orifice but does not reach it
Endoscopy
Lesion margin does not contact the orifice
Note: Oung 2020 ESD series included contact lesions only (Type 0 excluded). Often managed like routine cecal ESD.
Type 1
Touches orifice
Relation
Reaches the border of the appendix but does not enter the orifice
Endoscopy
Lesion margin contacts the appendiceal orifice
Note: Strategy A (incise the appendiceal side first) is usual; switch to Strategy B if fibrosis limits access.
Type 2
Partial invasion, edge visible
Relation
Enters the orifice; transition to normal appendiceal mucosa is discernible in the lumen
Endoscopy
Appendiceal-side margin of the lesion can be identified
Note: En-bloc ESD rates of 83.3–100% are often reported. Strategy B is primary; Strategy A if submucosal lift is good.
Type 3
Deep invasion, edge not seen
Relation
Enters the orifice deeply; tumor edge cannot be observed
Endoscopy
Appendiceal-side margin is not visible inside the orifice
Note: Surgery is usually preferred. ESD series report high perforation rates (54.5% in Oung 2020). Jacob 2016 excluded Type 3 without prior appendectomy.
After appendectomy
Type 3a
Deep invasion after appendectomy
Relation
Deep invasion at the area of previous appendectomy (residual appendiceal stump)
Endoscopy
Same deep extension pattern as Type 3, but appendectomy has been performed
Note: Short residual stump favors en-bloc resection. Included with Type 3 in Oung 2020 DCT-ESD series; traction helps.
Oung 2020, Fig. 2, Not original, CC BY-NC-ND
Reference
Original article
Jacob H, Toyonaga T, Ohara Y, et al. Endoscopy 2016;48:829-836. Type 3a: Oung B, et al. Endosc Int Open 2020;8:E388-E395
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Decision support only. Follow current guidelines and local protocols. Classification definitions and terminology follow the original publication language.