80 Chapter 5 Figure 8. The relative size of epithelial tumor cells (SOS), compared to thickness of the knife blade used for cutting. In our opinion, the reported frequency of STAS in roughly half of all resected adenocarcinomas is an indication of the frequency of STAKS. STAKS is a frequent finding in the lung, not only in adenocarcinomas but also in squamous cell carcinomas and benign lung tissue. Further validation and consideration of STAS for implementation in routine diagnostic evaluation and reporting118, or recognizing it as a pattern of invasion in lung adenocarcinoma117, is not appropriate for an artifact (STAKS). The prognostic association of STAS is in line with that of more than 100 other prognostic factors associated with poorly differentiated lung adenocarcinoma, which are not used in routine diagnostic reporting. Moreover, the radiation oncologist defines radiotherapy target volumes on the basis of microscopic tumor extent114 119. In this context the STAKS pattern is likely to be a confounder, and we suggest that the target area for radiotherapy in lung cancer should not be based on displaced tumor cells during gross examination. Diaz and colleagues119 described the displacement of tumor cells in breast samples. Tumor cell displacement was observed in 32% of patients who had undergone large-gauge needle core biopsies. Remarkably, the incidence and amount of tumor displacement was inversely related to the time interval between core biopsy and excision. The authors suggested that tumor cells do not survive displacement. The wall
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