RT Journal Article SR Electronic T1 Rare Multi-system Histiocytic Sarcoma on F18-FDG PET/CT JF Journal of Nuclear Medicine Technology JO J. Nucl. Med. Technol. FD Society of Nuclear Medicine SP jnmt.121.262247 DO 10.2967/jnmt.121.262247 A1 Harwood, Matthew A1 Craig, Fiona E A1 Yang, Ming YR 2021 UL http://tech.snmjournals.org/content/early/2021/07/30/jnmt.121.262247.abstract AB 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.