Epithelioid Sarcoma on Fine Needle Aspiration Cytology: A Case Series Highlighting Diagnostic Challenges

Abstract

Background

Epithelioid sarcoma is a rare malignant soft tissue tumor that poses significant diagnostic challenges, particularly on fine needle aspiration cytology (FNAC), owing to its wide morphological variability and close resemblance to inflammatory and other neoplastic conditions. Early cytological recognition is crucial to avoid misdiagnosis and treatment delay.

Objective

To describe the cytomorphological spectrum of epithelioid sarcoma on FNAC and to highlight the diagnostic utility and limitations of FNAC through a case series with histopathological and immunohistochemical correlation.

Methods

This case series includes three patients with epithelioid sarcoma presenting at different anatomical sites with variable clinical duration and presentation. FNAC was performed in all cases, followed by histopathological examination of biopsy or excision specimens. Cytological findings were systematically correlated with histopathology and immunohistochemistry.

Results

FNAC smears across all cases were moderately to highly cellular and demonstrated dispersed epithelioid to plasmacytoid tumor cells with occasional spindle-shaped cells in a necrotic background. The tumor cells exhibited abundant cytoplasm, eccentrically placed nuclei, vesicular chromatin, and prominent nucleoli, with mild to marked nuclear pleomorphism. Histopathological examination revealed nodular tumors composed of sheets and nests of plump oval to polygonal cells with eosinophilic cytoplasm, frequent mitotic activity, areas of myxoid change, and extensive necrosis. Immunohistochemistry showed tumor cell positivity for cytokeratin and epithelial membrane antigen (EMA) in all cases, with complete loss of nuclear INI1 (SMARCB1) expression, confirming the diagnosis of epithelioid sarcoma, including both conventional and proximal-type variants.

Conclusion

Epithelioid sarcoma remains a significant diagnostic challenge on FNAC due to its cytomorphological heterogeneity and overlap with other malignancies. The presence of plasmacytoid or rhabdoid cells, necrotic background, and mixed cellular population on cytology should raise suspicion for this entity. FNAC serves as a valuable initial diagnostic tool; however, definitive diagnosis requires histopathological confirmation and immunohistochemical correlation, particularly demonstration of INI1 loss. Awareness of the cytological spectrum of epithelioid sarcoma is essential for accurate diagnosis and timely management.