Key result
Diagnosing clear cell sarcoma in malignant effusions relies on cytology, melanocytic markers, and EWSR1 detection.
Why the study?
Clear cell sarcoma of soft tissue with malignant effusion is rare and clinically aggressive, posing a diagnostic pitfall due to cytomorphologic features overlapping with metastatic melanoma and carcinoma.
Case Report (n=1)
Highlights the diagnostic approach for clear cell sarcoma of soft tissue presenting with malignant effusion, utilizing cytology, immunocytochemistry, and molecular pathology to differentiate it from melanoma and carcinoma.
Raises awareness of CCSST in malignant pericardial effusions; leaves open molecular validation to distinguish from melanoma in cytology.
Clear cell sarcoma of soft tissue (CCSST) with malignant effusion is a rare yet clinically aggressive appearance, which may pose a diagnostic pitfall with its overlapping cytomorphologic features with metastatic melanoma and carcinoma. In this article, we reported a case with metastatic clear cell sarcoma of soft tissue with positive cytological findings in the sputum, as well as the peritoneal fluid and pericardial fluid. The cytological findings were compared and contrasted with cases reported in the literature. Malignant effusion cytology, variable positivity of melanocytic immunocytochemistry markers (namely S100, SOX10, Melan‐A, HMB‐45) and confirmatory molecular pathology techniques (e.g., detection of underlying EWSR1 gene rearrangement by fluorescent in situ hybridization or by reverse transcription polymerase chain reaction for EWSR1‐ATF1 gene fusion) formed the key diagnostic approach of this entity.
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Wu et al. (2026) conducted a case report in Clear cell sarcoma of soft tissue (CCSST) with malignant effusion (n=1). Cytological and molecular diagnostic approach was evaluated. Diagnosis of clear cell sarcoma of soft tissue in malignant effusions relies on cytology, melanocytic immunocytochemistry markers, and molecular detection of EWSR1 gene rearrangement.
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