Clear Cell Borderline Tumor : Microinvasion
Clear cell borderline tumors must be thoroughly sampled to rule out areas of destructive stromal invasion. Small foci of microinvasion are still compatible with the diagnosis of clear cell borderline tumor. In this case, a small 0.3 mm focus of microinvasion was found (round nodule in the upper left) in 18 sections submitted for a 10 cm tumor. The remainder of the tumor was composed of tubulocystic and simple papillary structures. There is multilayering and nuclear pseudostratification with mild to moderate cytologic atypia. Mitotic activity is not increased.