[Rare primary proximal epithelioid sarcoma in skull base: clinical analysis of four cases]

Objective: To report the clinical and pathological features of primary proximal epithelioid sarcoma (PES) in skull base. Methods: The clinical and pathological features of four cases of PES in skull base from Sanbo Brain Institute of Capital Medical University and Kunming Sanbo Brain Institute were analysed retrospectively. Results: Three cases was female, and one male, the age ranged from 46 to 52 years.All cases occurred in skull base, and sellar region was the main site of involvement.Under the microscope, the tumor cells characterized by epithelioid cell changes, with or without rhabdoid tumor cells.Mitotic figure was active.Immunohistochemical staining showed that AE1/AE3, EMA and CD34 were variously expression in tumor cells.INI-1 protein was lost in all cases.Three cases were detected by FISH, and INI1 (22q11.2) gene locus was absent in them.Three patients died less than 3 months after surgery, and case 4 was under treatment after five months of surgery. Conclusions: Primary PES in skull base mostly occurs in sellar region and its clinical prognosis is poor.It features with epithelioid/rhabdoid tumor cells with lack granuloma structure as distal ES.It has epithelial and mesenchymal differentiation characteristics.CD34 is always positive.INI1 gene deletion and protein loss expression are characteristic molecular alteration of PES.