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M. Hameed



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    OA 18 - Lung Cancer Pathology and Genetics (ID 687)

    • Event: WCLC 2017
    • Type: Oral
    • Track: Biology/Pathology
    • Presentations: 1
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      OA 18.06 - Three-Dimensional Assessment of Spread Through Air Spaces in Lung Adenocarcinoma: Insights and Implications (ID 8826)

      15:25 - 15:35  |  Author(s): M. Hameed

      • Abstract
      • Presentation
      • Slides

      Background:
      Tumor spread through air space (STAS) is a newly recognized form of invasion in lung adenocarcinoma and squamous cell carcinoma and growing evidence shows it is associated with recurrence and survival. The observation that tumor STAS clusters/nests or single cells within air spaces on two-dimensional H&E slides raised the question of how these cells could survive within air spaces without a vascular supply and this has led some to speculate STAS is an artifact. Herein, we perform the high resolution-high quality 3D reconstruction and visualization of normal lung and tumor in a lung adenocarcinoma to investigate the invasive pattern of STAS.

      Method:
      A formalin-fixed paraffin embedded block of invasive adenocarcinoma with micropapillary pattern and extensive STAS was studied. Following our histology 3D reconstruction standard procedure, 3D reconstruction was performed for analysis from 200 serial sections of H&E stained 20x (0.5um/pixel resolution) whole slide images. The relationship to alveolar walls between micropapillary structures within the tumor and STAS clusters in lung parenchyma distant from the tumor was evaluated.

      Result:
      3D reconstruction and analysis demonstrated the following novel features – a) in the main tumor area, micropapillary structures within airspaces were connected to alveolar walls, b) unlike in 2D evaluation where STAS appeared as ‘free-floating’ micropapillary clusters, in 3D evaluation many STAS clusters within air spaces are attached to alveolar walls, and c) STAS clusters that appear ring-like in 2D by 3D evaluation they are actually balls of tumor cells surrounding a central space.

      Conclusion:
      Our 3D reconstructed image analysis for the first-time demonstrates that most STAS cells are not ‘free-floating’, rather attached to the alveolar walls. In addition within the main tumor micropapillary clusters are attached to alveolar walls. These findings raise an intriguing hypothesis that STAS cells are clusters of tumor cells spread within alveolar spaces in a non-contiguous fashion to reattach to the alveolar walls at a distance possibly by co-option of alveolar wall capillaries to support their growth. This form of spread is analogous to the phenomenon of vascular spread where tumor cells spread freely within blood vessels to distant sites where they attach to endothelium and extravasate through the vessel walls to form metastases. It is possible the ball-like configuration of STAS clusters may facilitate movement through alveolar spaces distant from the main tumor. The frequent alveolar wall attachment of STAS observed on serial 3D imaging disputes the concept this is an artifact.

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