Unveiling Histiocytic Sarcoma: A Rare Case of Diagnostic Complexity and Therapeutic Resistance.

Histiocytic sarcoma (HS) is a rare and aggressive hematological malignancy. It is derived from the lineage of macrophages or monocytes. HS commonly presents as a mass in areas such as the gastrointestinal tract and soft tissues. This case highlights the clinical challenges in diagnosing and managing HS in a 37-year-old female patient. Accurate diagnosis relies on immunohistochemistry and molecular studies, while treatment outcomes remain suboptimal. The patient underwent multimodal therapies, including chemotherapy, targeted therapy, and radiation therapy, with disease progression observed despite treatment. This report underscores the need for novel approaches to improve outcomes in HS and the role of ARID2 mutations, which in our case limits the applicability of immune checkpoint inhibitors in disease management.