Can You Detect Spread Through Air Spaces (STAS) in Lung Needle Core Biopsies? An Initial Investigation

• Published in: American journal of clinical pathology 2019-09, Vol.152 (Supplement_1), p.S48-S49
• Main Authors: Pillappa, Raghavendra, Robila, Valentina, King, Caleb, Kraft, Adele
• Format: Article
• Language: English
• Subjects: Biopsy; Growth patterns; Lung cancer; Parenchyma; Tumors
• ISSN: 0002-9173; 1943-7722
• DOI: 10.1093/ajcp/aqz113.029

Abstract Objectives The debate of spread through air spaces (STAS) as a newly described pattern of invasion in lung cancer is ongoing. Some authors argue that the inclusion of STAS in the CAP synoptic template is premature and controversial as it is difficult to exclude an artifactual process. However, assessment of STAS in needle core biopsies has not been pursued. Hence, we intended to evaluate STAS in needle core biopsies, with an added emphasis on the specimen requirements for detection. Finally, correlation with the corresponding available resections was performed. Methods Fifty-four needle core biopsies of adenocarcinomas were examined by three pathologists. For each case, the extent of both tumor (1-12 mm) and nonneoplastic alveolated parenchyma (NNT) (2-6 mm) was measured. STAS was defined as presence of only micropapillary clusters, solid nests, and single cells in NNT adjacent to the main tumor. Corresponding lung resections available in 12 cases were also examined. Results Nests highly suspicious for STAS were demonstrated in 4 (7%) cases, predominantly micropapillary clusters and single cells. Of those, only one case had a surgical resection and showed STAS. When the NNT was present, then absence of STAS was determined in 20/54 (37%) tumors, all exhibiting a lepidic/acinar growth pattern. Finally, the presence of STAS could not be evaluated in 30 (55%) cases. This was due to extensive core fragmentation, sampling only from the center of the tumor, with no adjacent NNT, necrosis, or fibrotic background. Conclusion STAS evaluation may be performed in core needle biopsies and depends on the core quality and tumor/NNT content. Despite appropriate material, STAS was not identified in approximately one-third of cases. Rare cases with small groups suspicious for STAS were seen. These findings may provide additional information for further therapeutic/surgical guidance.