Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 10 4 2018 12 29 40 46 Abolfazl Salari Cancer Research Center, Cancer Institute, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences. Hana Saffar Anatomical and clinical pathology, department of pathology, cancer institute, IKHC, Tehran University of Medical Sciences(TUMS) Mohammad Shirkhoda Department of Oncosurgery, Cancer Research Center, Cancer Institute, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences. 2018 10 24 2018 12 08 Interdigitating dendritic cells (IDCs) act as antigen-presenting cells (APC) of the immune system and have the ability to stimulate T cells. These cells are mostly seen in the paracortex of the lymph node. The interdigitating dendritic cell sarcoma (IDCS) originating from the IDC is an extremely rare tumor. This tumor is observed in both lymph nodes and non-lymph nodes. This malignancy is difficult to diagnose due to its rarity, and thus far no guideline has been established for its treatment. However, it seems that the best treatment for this malignancy is radical resection of the tumor. Meanwhile, the role of chemotherapy and radiotherapy in the survival and recurrence of the tumor is not clear. In this study, we present a case of IDCS originating from a cervical lymph node, which was first exposed to mass resection, with IHC evaluation revealing negative CD1a, CD3, CD20, CD23, and CD21 factors and positive S100 and LCA factors. After confirming the diagnosis,modified radical neck dissection was performed. In the next stage, the patient underwent chemotherapy with an R-CHOP regimen (Rituximab, Cyclophosphamide, Doxorubicin Hydrochloride, Oncovin, Prednisone) and neck radiotherapy. 18 months after the formation of the tumor, no sign of recurrence or metastasis was observed in the patient. https://bccr.tums.ac.ir/index.php/bccrj/article/view/305