| Tang classification | Goblet cell carcinoid | Carcinoid | Adenocarcinoma |
| Clinical features |
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| Age | 5th - 6th decade | 4th decade | 7th decade |
| Carcinoid syndrome | No | Yes | No |
| Primary symptoms | Acute appendicitis | Acute appendicitis | Mass |
| Gross appearance | >2 cm, ill defined thickening | <2 cm | >2 cm, well defined mass |
| Microscopic appearance |
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| Morphology | Clusters of goblet or signet-ring cells separated by fibrosis/pools of mucin | Nests of small cells | Well-formed glands to sheets of poorly differentiated signet-ring cells |
| Atypia | Minimal | Minimal | Marked |
| Mitosis | Rare | Rare | Increased |
| Vascular and perineural invasion | Present | Absent | Present |
| Infiltrative margins | Present | Absent | Present |
| Special stains |
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| Argyrophil | Positive | Positive | Usually negative |
| Argentaffin | Negative | Positive | Negative |
| Mucicarmine/PAS/PASD | Positive in goblet cells | Negative | Positive |
| IHC |
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| CEA | + | − | + |
| CDX2 | + | − | + |
| CAM5.2 | + | − | + |
| CK20 | +/− | − | + |
| CK7 | +/− | − | − |
| CK19 | + | − | − |
| Neuroendocrine markers | +/− | +/− | − |
| Math1 and HD5 | + | − | + |
| p53, p16 | − | − | + |
| Molecular pathology |
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| DPC4, Kras, β-catenin mutation and p53 over expression | − | − | + |