Carcinosarcoma of the pancreas: comprehensive clinicopathological and molecular characterization

Background: Carcinosarcoma of pancreas is a rare subtype of pancreatic cancer. The aim of this study was to comprehensively elaborate the clinicopathological and molecular features of this rare malignancy. Methods: Patients who were diagnosed with carcinosarcoma of the pancreas were retrospectively identified from pathology database of a single institution between 2012 and 2018. Results: A total of nine patients were identified. Pathological examination of tumor tissues from included patients showed coexisting carcinomatous and sarcomatous components. These two components were distinguished by mutually exclusive expression of cytokeratin and vimentin. The sarcomatous tissue exhibited more extensive proliferation, as revealed by Ki67 staining, and necrosis compared with the carcinomatous counterpart. Genomic analysis of tumor tissues for two patients demonstrated hotspot mutation at KRAS and TP53. Carcinomatous and sarcomatous components were separately obtained via laser captured microdissection in one patient, and mutations of driving genes were highly concordant between them. Besides, immunostaining of frequently-altered tumor suppressor genes for these two components suggested consistent expression patterns. The median overall survival for six patients with adequate follow-up was 14 months. Conclusion: Carcinosarcoma of the pancreas represent a rare malignancy with distinct histological characteristics. Genomic and molecular analysis suggested monoclonal origin of carcinomatous and sarcomatous components.