Interdigitating Dendritic Cell Sarcoma in Upper Arm Misdiagnosed as Ruptured Epidermal Inclusion Cyst

Interdigitating dendritic cell sarcoma (IDCS) is an extremely rare neoplasm that usually arises in lymph nodes, but also can exist extranodal sites. This report about a case study of IDCS the upper arm skin with axillary node metastasis. A 66-year old woman had slowly growing mass tenderness sensation on her right was being injected triamcinolone acetonide at local clinic. The presumptive diagnosis ruptured epidermal inclusion cyst, and empiric antibiotic therapy done; however, she poor respondence to therapy. Therefore, magnetic resonance imaging, incisional biopsy, positron emission tomography-computed tomography, bone scan were performed malignant tumor diagnosed. She received surgical resection dissection axilla. No adjuvant chemotherapy done. Although rare, this suggests should be considered differential untreated atypical early biopsy performed.