Figure 1:

Artifacts: A) More than four air spaces away from the tumor edge are clusters of tumor cells with ragged edges. These tumor clusters are isolated distantly away from the tumor edge lacking spread in air spaces continuously from the tumor edge. B) Higher power shows this tumor cluster has jagged edges suggesting an artifact from a knife cut. C) These tumor cells are situated on the edge of the tissue and were located far away from the border of the tumor. D) Along the edge of the tumor clusters is a sharp flat edge that indicates a knife cut and the tumor cells appear compressed against the tissue rather than being contained within the tissue.