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 in 18 sections submitted for a 10 cm tumor. This image is from the microinvasive focus. The remainder of the tumor was composed of tubulocystic and simple papillary structures.