Common clinicopathological and immunological features of sarcomatoid carcinoma across organs: A histomorphology‐based cross‐organ study

Abstract Sarcomatoid carcinoma (SC), which can occur in any organ, is a rare disease. To elucidate common characteristics of SC beyond organs, we evaluated clinicopathological and immunological features of SC defined by the single histological criterion beyond organs compared to randomly matched conventional carcinoma (non‐SC) adjusted for the disease stage. Immunological features were assessed by multiplex immunohistochemistry, comparing immune cell density in tumor tissues and tumor programmed death‐ligand 1 (PD‐L1) expression. A total of 101 patients with SC or non‐SC (31 lung, 19 esophagus, 22 pancreas, 15 liver, 4 bile duct, 6 kidney, 2 uterus and 2 ovary) were identified among 7197 patients who underwent surgery at our institute (1997‐2020). SC was significantly associated with worse survival (HR: 1.571; 95% CI: 1.084‐2.277; P = .017). The frequency of postoperative progression within 6 months was significantly higher for SC patients (54% vs 28%; P = .002). The immune profiling revealed the densities of CD8 + T cells (130 vs 72 cells/mm 2 ; P = .004) and tumor‐associated macrophages (566 vs 413 cells/mm 2 ; P < .0001) and the tumor PD‐L1 expression score (40% vs 5%; P < .0001) were significantly higher in SCs than in non‐SCs. Among 73 SC patients with postoperative progression, multivariate Cox regression analysis showed that immunotherapy tended to be associated with favorable survival (HR: 0.256; 95% CI: 0.062‐1.057; P = .060). Collectively, SCs shared clinicopathological and immunological features across organs. Our study can initiate to standardize the pathological definition of SC and provide a rationale for the investigation and development for this rare disease in a cross‐organ manner.