Pulmonary loose tumor tissue fragments and spread through air spaces (STAS): Invasive pattern or artifact? A critical review

These data are summarized in this review and support the conclusion that the inclusion of STAS in the WHO classification for lung cancer as a pattern of invasion was premature and erroneous. In our opinion, these tumor cell clusters or loose cells appear to be simply an artifact, although one which may or may not pinpoint to a high-grade tumor with discohesive cells and adverse prognosis.