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. Author manuscript; available in PMC: 2022 Apr 1.
Published in final edited form as: J Thorac Oncol. 2020 Dec 24;16(4):619–629. doi: 10.1016/j.jtho.2020.12.005

Figure 1. Comparison of STAS and Artifact on Frozen Section and Frozen Section Permanent Slides.

Figure 1.

Examples highlighting the morphologic spectrum of STAS and artifact on Frozen Section (FS) and FS permanent (FSP) are shown, including foci considered to be equivocal for STAS. A FS showing a cohesive small tumor cluster spatially distant from the edge of the tumor (A) is confirmed on FSP (B) to be STAS in micropapillary clusters and small solid nests. Alternatively, FS showing an irregular tumor cluster with jagged and sharp contours (C) is confirmed to be artifact on FSP (D), which further highlights the irregular contours and dyshesive morphology. A third FS (E) shows a single focus of tumor that appears to be micropapillary or solid STAS on the right (arrow), but also a more jagged focus of tumor on the left (arrowhead), which is highlighted on higher power in the inset and in isolation; this is considered to be equivocal for STAS on FS. Examination of the corresponding FSP (F) confirms the micropapillary STAS (arrow), but also reveals that the tumor cluster determined to be equivocal is likely a mixture of true micropapillary STAS and dyshesive irregular artifact that is intermixed (arrowhead and inset). Similarly, a fourth FS (G) shows a focus of linear epithelial strips definitive for artifact on the right (arrowhead), along with an indeterminate cluster composed of linear strips and small epithelial tufts (arrow and inset). Examination of the corresponding FSP (H) confirms that the focus determined to be equivocal on FS as definitive for STAS (arrow and inset).