Unusual EMA and pan-keratin negative epithelioid sarcoma
Andrea Alpeza1✉, Katarina Gregorović1, Darija Alpeza2,3, Zlatka Radičević2,3, Nikolina Kurtović2, Luka Klobučarić2, Branka Lončar1,3
- 1 Clinical Institute of Clinical Cytology, Clinical Hospital Center Osijek, Croatia
- 2 Clinical Institute of Pathology and Forensic Medicine, Clinical Hospital Center Osijek, Croatia
- 3 J.J. Strossmayer University in Osijek, Faculty of Medicine Osijek, Croatia
Received 14 October 2026 · Accepted 14 October 2026 · Published 14 October 2026
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Key messages
- Epithelioid sarcoma can present with unusual absence of EMA and pan-keratin expression.
- SMARCB1 loss is a key feature in this rare malignant neoplasm with rhabdoid characteristics.
- Accurate diagnosis requires exclusion of other primary tumor sites and expert pathological consultation.
Abstract
Introduction
Epithelioid sarcoma is a rare malignant tumor typically positive for EMA and pan-keratin, often showing loss of SMARCB1 expression. This case report presents a 65-year-old female patient with a 5.2 cm abdominal mass detected by ultrasound.
Materials and methods
Cytopuncture and core biopsy were performed under CT control. Cytological and histological analyses were conducted, including immunocytochemistry and immunohistochemistry to characterize the tumor cells.
Results
Cytology revealed monomorphic poorly differentiated malignant cells forming clusters with a homogeneous substance. Immunocytochemistry showed weak S100 positivity and negative CK7 and CK20. Histology showed uniform cells with scant cytoplasm, negative for multiple markers including EMA and pan-keratin, but positive for CD99. Expert consultation diagnosed a SMARCB1-deficient malignant neoplasm with rhabdoid features and absence of EMA and pan-keratin expression, consistent with keratin-poor epithelioid sarcoma after excluding other primary tumor sites.
Conclusion
Further research is needed to better understand the role of SMARCB1 loss in tumor immunogenicity to develop optimal immunotherapeutics and new treatment strategies for these aggressive tumors.
Original poster
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