Rare Multi-system Histiocytic Sarcoma on F18-FDG PET/CT.

Histiocytic sarcoma (HS) is a rare malignancy with morphological and immunophenotypic features of histocytes. We present a case of histiocytic sarcoma with multisystem involvement, including an obstructing pancreatic head mass. F18-FDG PET/CT is a valuable tool in staging and assessment of response to therapy in this rare entity. Knowing the diverse metastatic pattern of HS will help avoid imaging pitfalls for the diagnosis after pathologic diagnosis is made.