RESUMO
INTRODUCTION: follicular dendritic cell sarcoma (FDC sarcoma) is an uncommon neoplasm derived from FDC present in lymphoid follicles. It usually presents in lymph nodes, being extranodal location a very unusual event. CASE REPORT: A 78 year old female, with prior left nephrectomy for invasive urothelial carcinoma, consulted for genitorragia. At examination, a polypoid vaginal lesion, measuring 3.5 cm in diameter was discovered. It was reported as squamous cell carcinoma in incisional biopsy. A polipectomy was performed. Examination of resected specimen showed a tumor having pushing edges, arranged in a solid pattern with spindle and epithelioid cells, having a syncytial appearance, diffusely sprinkled with numerous lymphocytes and granulocytes. At immunohistochemistry neoplastic cells were positive for vimentin, CD 68, CD 21 and fascine, and focally positive for S-100 and CD45. Occasional scattered neoplastic cells expressed CD30 and CD 23. They were negative for CD3, CD20, myeloperoxidase, AE1 / AE3, EMA, HMB45, Melan A, desmin, Chromogranin, CD1a and CD35. Infiltrating lymphocites were mainly of T cell lineage (CD3 +). DISCUSSION: We report a case of FDC sarcoma in an unusual location, being to our knowledge, the first one at this site. The fact of having a prior neoplasia posed additional difficulties in differential diagnosis. Histological findings with expression of a specific marker of FDC (in this case CD21) allowed us to establish an accurate diagnosis.