Submucosal gland differentiation and implications in esophageal basaloid squamous cell carcinomas

Esophageal basaloid squamous cell carcinoma (BSCC) is a heterogenous entity with multilineage differentiation. It lacks systematical analysis on submucosal gland differentiation (SGD) due to the histological diversity and low incidence of esophageal BSCC. This study aims to find the correlation of SGD and clinicopathological features. A total of 152 esophageal BSCCs were separated into three histological groups: pure, mixed, and borderline group. The clinicopathological features were compared between different groups. The prevalence of SGD was also compared between cases of different groups. A panel of antibodies were used to identify SGD. The pure group differed from the mixed and borderline groups in many aspects, lymph node metastasis (LNM), cancer embolus, perineural invasion, and advanced stage occurred less frequently in the pure group (P<0.01). The pure group had a better but statistically insignificant overall survival (P=0.097). The squamous cell carcinoma (SCC) component or focal squamous differentiation was present in metastatic lymph nodes in almost all mixed BSCCs (95.7%, 22/23) with LNM. The LNM rate of superficial (T1b) BSCCs (17.6%, 6/34) was comparable to that of superficial (T1b) SCCs (18.5%, 57/308). However, LNM exclusively occurred in superficial mixed (3/5) and borderline (3/10) BSCCs. The IHC results demonstrated a prevalence of SGD in pure group (77%, 43/56). SGD is considered to be a favorable factor, while the squamous differentiation or invasive SCC component is an adverse factor in esophageal BSCCs. Refinement of classification is a promising way to improve patient management.