81 yrs old female with history colorectal polyps (different kinds of adenomas NOT INCLUDED there) presented with mediastinal mass.
Core biopsy was taken (included).
After diagnosis of "thymoma A" the tumor was resected.
MACRO: Greyish/white, fleshy, encapsulated tumor 9,5x9x4,5 cm.
HISTO: Encapsulated nodules and diffuse zones: solid, trabecular, nested, NET like, focally spindled. 1 single nodule (block 10) and in part focal areas in another blocks are BIPHASIC:
- epithelioid larger cells in nests;
- in between more "lymphoid" or "blastic" or "immature" appearing still epithelial cells (PanCK+).
Mitoses focally up to 8/10 HPF.
IH: Predominantly PanCK+ CK5+ p63+ tumor, but still BIPHASIC in block 10 and small cells seems to be p40/p63/CK5(-) but PanCK+ (as histology pattern was).
FULL: PanCK+; CK5/p63/p40+; Chromogranin A/Synaptophysin(-); CD5/CD117/S100/CD56(-); Ki67 heterogenous up to 30%.
DIAGNOSIS: Thymoma A with multifocal microscopic transcapsular spread ((9,5 cm); pT1a; Masaoka-Koga IIb; minimal distance form margin <0,1mm).
QUESTIONS:
- Biphasic pattern in single thymoma nodule (but not B component- without blasts or lymphos);
- High Ki67 index and focally visible mitotic activity: is it enough and more appropriate to call it "atypical thymoma A"?
Thymoma A: ATYPICAL/BIPHASIC?