Table 3 Pitfalls in sTIL assessment in breast cancer slides identified from cases showing the highest variation in 3 ring studies (RS)—technical factors.
From: Pitfalls in assessing stromal tumor infiltrating lymphocytes (sTILs) in breast cancer
Pitfall | Frequency seen | Recommendation |
|---|---|---|
Technical factors | 13/26 (50%) | |
Poor quality slides / Histological artifacts secondary to prolonged ischemic time, poor fixation or issues during processing (Fig. 5a) | RS1: 0 RS2: 0 RS3: 11/13 (85%) | Thankfully, in the current era, with greater awareness and monitoring of preanalytical and analytic variables, these sorts of poor quality H&E slides should not be an issue. If presented with such a case, only intact, morphologically assessable areas should be included in sTIL score. If applicable, one can cut and stain an additional section or select a different block for assessment. |
Crush artifact (Fig. 5b) | RS1: 1/7 (14%) RS2: 0 RS3: 0 | More commonly seen in biopsy samples, crush artifact can compromise sTIL assessment. Areas of crushing should be excluded from sTIL evaluation. |
Out-of-focus scan (Fig. 5c) | RS1: 1/7 (14%) RS2: 1/6 (17%) RS3: 0 | As part of a study one may struggle with scoring an out-of-focus scan. In clinical practice, however, particularly as sTILs are poised to impact patient management, there is no good justification to not rescan the slide. If this is not a possibility most computer programs have some capability of image correction. |
