Follicular Dendritic Cell Sarcoma of Gastrointestinal Tract: an Uncommon Lesion, Commonly Missed.

INTRODUCTION: Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm, accounting for only 0.4% of soft-tissue sarcomas. It shows both nodal and extranodal involvement. Considering the rarity and difficulties in diagnosing this tumor, we consider it very important to share our experience of diagnosing FDCS. Its correct diagnosis cannot be overemphasized as the treatment and prognosis of FDCS are very much different from tumors which come in its differential diagnosis.
MATERIAL AND METHODS: We are presenting eight cases of extranodal FDCS in gastrointestinal tract diagnosed at our center in a period of 3 years (Feb 2015 to Feb 2018). Presenting complaints, demographic details, gross description, histologic features, immunostain results, and clinical follow-up were evaluated.
RESULTS: Four patients were females and four were males. Tumor ranged in size from 5.5 to 35 cm. In five cases, tumor cells were arranged in storiform and whorling pattern. Lymphocytes were seen sprinkled in between these cells. In one case, lymphocytic infiltrate was extensive. Giant cells and frequent mitoses were noted in two cases. One case showed extensive necrosis. Tumor cells were strongly and diffusely positive for CD21 and CD35. Mean follow up of 11.8 months (range 01 to 24 months) was noted.
CONCLUSION: FDCS is a rare tumor having distinct morphology and phenotype which if known can be correctly diagnosed. Therefore, knowledge of its varied location, morphology, and phenotype is very important to correctly diagnose this tumor and to prevent misdiagnosis and mistreatment.