Table 3.
Morphologic Criteria to Distinguish ErbB/Ras from Wnt Pathway Tumors
| Criterion | ErbB/Ras pathway | Wnt pathway |
|---|---|---|
| Histological pattern | Solid | Branched ductules/acinar component |
| Keratinization | Rarely present | Frequently present |
| Myoepithelium | Not present | Frequently present;* |
| Stroma | Scanty | Dense |
| Inflammatory infiltrates | Present only in necrosis | Frequently present |
While myoepithelial spindle cell tumors and adenomyoepitheliomas represent only 15% of the Wnt pathway tumors, a basal myoepithelial layer is observed in more than 50% of the Wnt pathway tumors.