Primary Histiocytic Sarcoma of Bone with Disseminated Involvement - Initial Presentation Mimicking Multiple Myeloma: The Atypical Face of a Rare Neoplasm

Histiocytic Sarcoma (HS) is an uncommon malignancy derived from macrophage/dendritic lineage cells and accounts for less than 1% of hematologic tumors. Due to its rarity, little is known about its clinical-biological behavior and therapeutic recommendations have not been standardized so far. In addition to lymph node enlargement most cases present extranodal involvement, especially in the gastrointestinal tract, skin and soft tissues. Bone involvement is usually described in association with systemic disease and in advanced stages. Here we describe a case of patient with HS with primary bone involvement and multiple osteolytic lesions and bone fractures in the absence of another organs involvement. A male patient presented with an aggressive disease with rapid progression and his disease was unresponsive to standard therapy. Although rare, this kind of HS presentation should fall within the scope of differential diagnosis of other neoplasms with widespread bone involvement such as multiple myeloma and bone metastasis from solid tumors as the prostate, breast and lungs. Hemoglobin Concentration; RDW: Red Cell Distribution Width; WBC: White Blood Count; TIBC: Total Iron-Binding Capacity; ESR: Erythroid Sedimentation Rate; CRP: C-Reactive Protein; Ca: Calcium; HIV: Human Immunodeficiency Virus; MRI: Magnetic Resonance Imaging; CT: Computerized Tomography; H&E: Haematoxyline & Eosin staining; TdT: Terminal Deoxynucleotidyl Transferase; 18-FDG-PETCT: 18-Fluorodeoxyglucose-Computerized Tomography With Positron Emission; Max: Maximum; SUV: Standardized UpTake Value; CHOEP: Cyclophosphamide, doxorubicin, Oncovin, Etoposide and Prednisone; G-CSF: Granulocyte Colony Stimulating Factor; OS: Overall Survival; ICE: Ifosfamide, Carboplatin and Etoposide