티스토리 뷰
| Stage | Definition |
| I | Macroscopically and microscopically completely encapsulated |
| IIA | Microscopic transcapsular invasion |
| IIB | Macroscopic invasion into surrounding fatty tissue or grossly adherent to but not through mediastinal pleura or pericardium |
| III | Macroscopic invasion into neighboring organs (ie, pericardium, great vessels, or lung) |
| IVA | Pleural or pericardial dissemination |
| IVB | Lymphogenous or hematogenous metastasis |
| WHO histologic classificationType | Histologic description |
| A | Tumor in which foci having features of type A thymoma are admixed with foci rich in lymphocytes |
| B1 | Tumor resembles normal functional thymus; combines large expanses having an appearance practically indistinguishable from that of normal thymic cortex with areas resembling thymic medulla |
| B2 | Tumor in which neoplastic epithelial component appears as scattered plump cells with vesicular nuclei and distinct nucleoli among a heavy population of lymphocytes; perivascular spaces are common and sometimes very prominent; a perivascular arrangement of tumor cells resulting in a palisading effect may be seen. |
| B3 | Thymoma predominantly composed of epithelial cells having a round or polygonal shape and exhibiting no or mild atypia; they are admixed with a mild component of lymphocytes, resulting in a sheetlike growth of the neoplastic epithelial cells |
| C | Thymic tumor exhibiting clear-cut cytologic atypia and a set of cytoarchitectural features no longer specific to the thymus, but rather analogous to those seen in carcinomas of the other organs; type C thymomas lack immature lymphocytes; whatever lymphocytes may be present are mature and usually admixed with plasma cells |