A case report of small round cell tumor of palm: A difficult code to decipher on cytology

INTRODUCTION: Small round cell tumors (SRCT) are difficult to sub categorise on fine-needle aspiration cytology (FNAC) samples as they are rare and it is difficult for cytopathologists to obtain enough experience for rendering reliable diagnoses. Various sub categories of SRCTs are morphologically very similar. Many SRCTs do not have specific antigens which could be demonstrated with immunocytochemistry (ICC) or they lose them when poorly differentiated. Besides, cross-reactivity exists between some SRCTs. Suboptimal FNAC sampling from a heterologous component and unstandardized performance of ICC contributes to the pitfalls. PRESENTATION OF THE CASE: A 40-year-old male presented with a swelling measuring 3 cm in diameter on palmar aspect of right-hand. Magnetic resonance imaging suggested cyst of tendon sheath. However, on cytology in combination with ICC, a diagnosis of non-lymphoid small round cells tumor was suggested, with confirmatory diagnosis on histopathology. CONCLUSION: FNAC assisted with ICC can be a rapid and economical diagnostic tool in cases of high-grade malignant tumors for which early diagnosis is extremely important.