S3904 A Rare Case of Histiocytic Sarcoma Presenting in the Terminal Ileum

Introduction: Histiocytic sarcoma (HS) is a rare mononuclear phagocytic or histiocytic tumor that can affect individuals from adolescence to old age with males more likely affected than women. HS can be unifocal or multifocal and can affect any organ in the body. The clinical presentation varies depending on the organ affected. Here, we report a rare case of a patient with right lower quadrant pain who was found to have histiocytic sarcoma in the terminal ileum. Case Description/Methods: A 37-year-old man with no past medical history presented to the hospital complaining of worsening right lower quadrant pain. Computed tomography abdomen/pelvis revealed a large malignant mass in the right lower quadrant cecal tip and the adjacent terminal ileum, in addition to a fluid collection extending through the right ventral wall. The patient was started on piperacillin/tazobactam. Interventional Radiology placed a right lower quadrant drain which drained 130 cc of purulent body fluid. The body fluid culture grew streptococcus anginosus, parvimonas micra, and bacteroides fragilis. The body fluid cytology was negative for malignancy. A colonoscopy revealed a normal appearing colon. However, upon intubating the terminal ileum, a frond-like, villous, and soft circumferential fifty millimeter obstructing mass was discovered. Biopsy of the mass revealed HS. Following the procedure, antibiotics were adjusted to ciprofloxacin and metronidazole, in line with sensitivities, and he completed a 7-day course. The patient did well and was discharged, drain in place, with close surgical and oncologic follow up and plans for surgical resection in 3 weeks. Discussion: HS is a rare disorder that most frequently affects the gastrointestinal tract, soft tissue, and skin. However, any organ can be involved. Treatment depends on whether HS is unifocal or multifocal: unifocal HS is treated surgically with adjuvant radiation therapy while multifocal HS is treated with chemotherapy. If left untreated, worsening organ dysfunction and death can occur. In our case, intubation of the terminal ileum allowed for successful biopsy and diagnosis. On literature review, there are limited reports of HS found in the ileum. This case highlights a rare diagnosis of HS in the terminal ileum, and the importance of terminal ileum intubation in comprehensive diagnosis and management.