Introduction: Extraskeletal Ewing sarcoma/PNET is a small round cell sarcoma showing gene fusions of
EWSR1-FLI1. A 28-year-old male patient presented with right ank pain and low gr Case Report: ade
fever since 15 days. On examination: a mass was palpable in the right hypochondrium. Provisional diagnosis of Liver abscess
has been made. USG abdomen shows features cystic lesion in the liver with internal septation ?Liver abscess /Hydatid cyst.
Intraoperatively, tumor was seen attached to upper pole of kidney. Since tumor was large, it was ruptured intraoperatively and
debulking surgery has been done. Under microscopy, tumor was arranged in sheets with intervening stroma showing
desmoplastic reaction. Perivascular pseudorosettes are seen. The diagnosis of malignant small round cell tumor has been
given. On immunohistochemistry, tumor cells are positive for Vimentin, CD99, NKX2.2 , FLI1, Neurolaments, Synaptophysin
with focal immunoreactivity for EMA, Pancytokeratin. Final diagnosis was EXTRASKELETAL EWING SARCOMA/PNET.
Discussion: Extra-skeletal Ewing sarcoma/PNET is malignant soft tissue tumor seen in chest wall, thigh, paravertebal region
etc. Retroperitoneum is a least common site. Most common presentation is swelling in the soft tissue with compressive
symptoms. Histologically, it is composed of undifferentiated small round cells.
Conclusion: Clinical examination and radiological ndings leads to ambiguous diagnosis in Ewing sarcoma/PNET. Hence
proper histopathological study is essential for nal diagnosis.
High-Grade Undifferentiated Small Round Cell Sarcoma with t(4;19)(q35;q13.1) CIC-DUX4 Fusion: Emerging Entities of Soft Tissue Tumors with Unique Histopathologic Features – A Case Report and Literature Review
