Background: This study aimed to comprehensively investigate the effect of spread through air spaces (STAS) on clinicopathologic features, molecular characteristics, immunohistochemical expression, and prognosis in lung adenocarcinomas (ADC) and squamous cell carcinomas (SQCC) based on the 8th edition AJCC/UICC staging system. Methods: In total, 303 ADC and 121 SQCC cases were assessed retrospectively. Immunohistochemical staining was performed for E-cadherin, vimentin, Ki67, survivin, Bcl-2, and Bim. Correlations between STAS and other parameters were analyzed statistically. Results: STAS was observed in 183 (60.4%) ADC and 39 (32.2%) SQCC cases. In ADC, the presence of STAS was associated with wild-type EGFR, ALK and ROS1 rearrangements, low E-cadherin expression, and high vimentin and Ki67 expression. In SQCC, STAS was associated with low E-cadherin expression and high vimentin and survivin expression. Based on univariate analysis, STAS was associated with significantly shorter disease-free survival (DFS) and overall survival (OS) in ADC. In SQCC, STAS tended to be associated with shorter OS. By multivariate analysis, STAS was an independent poor prognostic factor in ADC for DFS but not OS. Stratified analysis showed that STAS was correlated with shorter DFS for stage I, II, IA, IB, and IIA ADC based on univariate analysis and was an independent risk factor for DFS in stage I ADC cases based on multivariate analysis. Conclusions: Our findings revealed that STAS is an independent negative prognostic factor for stage I ADC using the new 8th edition AJCC/UICC staging system. Stage I patients with STAS should be followed up more closely and might need different treatment strategies.

Mixed epithelial and stromal tumors of the kidney (MESTK) are rare and recently defined entities that comprise both epithelial and stromal cells. MESTK is mostly benign; however, to date, 18 borderline or malignant cases have been reported. In this study, we report a case of carcinosarcoma exhibiting a large carcinoma and small sarcoma component, and review the relevant literature. The patient was a 59-year-old woman who presented with a large mass in the left kidney having solid and focal cystic components. The patient underwent left radical nephrectomy. The tumor was gray-white and solid-cystic, with a relatively clear boundary. Microscopically, the tumor revealed benign and malignant components. The benign component consisted of multiple tubules, variable-sized cysts lined with benign epithelium, and hyalinized stroma. The malignant component was composed of predominantly small cell neuroendocrine carcinoma and a small quantity of adenocarcinoma, squamous cell carcinoma, and sarcoma. Finally, a diagnosis of the malignant MESTK was made. Certain cases of borderline or malignant transformation of MESTK have been published, so it is important to enhance findings made by other studies.