Impacts of thoracoscopic surgery and high grade histologic subtypes on spread through air spaces in small stage I lung adenocarcinomas

Spread through air spaces (STAS) as a pattern of invasion in lung adenocarcinomas had been recognized by WHO in 2015. Moreover, STAS was associated significantly with aggressive micropapillary or solid components when presented predominant pattern in lung adenocarcinomas, which had a poor prognostic significance. Small amounts of micropapillary or solid with components could also reduce overall survival and recurrence-free survival but its impact on STAS is unknown now. Some studies have demonstrated manipulations of surgeons and pathologists could affect STAS but the degree of these impacts is not clear.

We reviewed resected small (≤ 2 cm) stage I invasive lung adenocarcinomas by thoracoscopic surgery at our institution from January 2017 to October 2018 (n = 277). Micropapillary or solid pattern was considered to be present when the subtype occupied at least 1% of the entire tumor. Lobectomy and segmentectomy were performed using three portals thoracoscopic surgery. Statistical analysis was performed to analyze the correlations of STAS and clinicopathological characteristics. Moreover, we also analyzed the correlated factors of STAS in solid nodules.

STAS was found in 59 of 163 (36.2%) lobectomy cases and 27 of 114 (23.7%) limited resection cases. Lobectomy group showed a higher incidence of STAS compared with limited resection group (p = 0.027), but the difference was disappeared in multivariate analysis, which showed that STAS was significantly correlated to solid nodules and presence of high grade histologic subtype (mircopapillary or solid). However, both lobectomy and presence of high grade histologic subtype were significantly correlated with STAS in solid nodules.

The small amounts of high grade histologic subtypes were also associated with STAS. Thoracoscopic surgery could affect STAS to some degree.