Follicular dendritic cell sarcoma of inguinal lymph node--a case report.

Follicular dendritic cell sarcomas (FDCS) are rare neoplasms that involve lymph nodes or extranodal sites. They show varied histological features and thus can be mistaken for carcinoma or sarcoma. Correct identification is important for further management. A 43-year-old Indian female presented with a three-month history of progressive swelling at the right inguinal region. It was excised completely and was reported as lymph node with metastatic poorly differentiated carcinoma based on Haematoxylin and eosin (H&E) stain findings. Computerized tomography (CT) scans of thorax, abdomen and pelvis were normal and did not reveal a primary site. Following this, the case was referred to one of the authors. The slides were reviewed and a variety of immunocytochemical markers were done. The tumour cells were negative for epithelial, melanocytic, neural, leucocyte and soft tissue tumour markers. They were immunopositive for CD21, CD35 and negative for CD68. Based on the immunocytochemical findings, a final diagnosis of FDCS was made. This case highlights the histological and immunophenotypical profile of a rare tumour which requires a high index of suspicion for diagnosis.