Table 1.

Region of interest types

Intra-tumoral stroma (aka tumor-associated stroma): Select ~3 ROIs
• Be sure to include regions with lymphocytes (TILs)
• If there are lymphocytic aggregates, make sure to capture both lymphocyte- depleted and lymphocyte-rich areas within the same ROI if possible
• Preferable to include some tumor in the same ROI — i.e. carcinoma cells as well
• If variable density within the slide, make sure to capture ROIs from different
Invasive margin (Tumor-stroma transition): Select ~2 ROIs
• If heterogeneous tumor morphology, sample from different tumor-stroma transitions for each
Tumor with no interveninq stroma: Select ~2 ROIs, if possible
• If heterogeneous tumor morphology, sample from different morphologies
• Be sure to sample from: vacuolated tumor cells, dying tumor cells, regions of
• Will be used to capture/assess intra-tumoral TILs and/or detect false positive Til- detections in purely cancerous regions.
Other regions: Select ~3-4 ROIs
• ~1 from “empty”/distant/uneventful stroma • ~1 from hyalinized stroma, if any • ~2 other regions:
⁰ Necrosis transition (including comedo pattern)  ⁰ Normal acini/ducts  ⁰ Blood vessels  ⁰ Others at patholoaist discretion