RESUMO
Ewing's Sarcoma is the second most common primary malignant bone tumor in children and young adults after osteosarcoma but exceptionally it can arise from extra skeletal sites also. Extra skeletal Ewing's sarcoma is of neuroectodermal origin and usually involves extremities, retroperitoneum and paravertebral regions. No case of extra skeletal Ewing's sarcoma involving perineum is yet reported. A 16 years old male patient admitted to colorectal surgery department of Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh in July 2015 having swellings in perineum as well as both inguinal regions. The swelling was near to anal verge. FNAC from perineal swelling and inguinal lymph node demonstrate small blue round cell tumor. After operation the tumor size was 5cm×4cm, cell type was malignant round cell arranged in sheet and perivascular forming rosette. Extra skeletal Ewing's sarcoma can be a differential diagnosis of soft tissue tumor arising in perineum.