INTERESTING IMAGE Simultaneous Brain and Lung Histiocytic Sarcoma Revealed on 18F-FDG PET/CT Yu Pan, MD, PhD, and Yifan Zhang, MD, PhD Abstract: A 52-year-old man with intermittent head motor tics, aphasia and right upper extremity weakness had an 18F-FDG avid left front lobe brain lesion, and a left upper lobe lung lesion on PET/CT. The brain lesion was surgically resected, and was diagnosed pathologically as a histiocytic sarcoma (HS). The lung lesion was also a HS via bronchial biopsy. HS is rare and generally involves nodes as shown on PET/CT in a few case reports. The current case with simultaneous brain and lung HS lesions adds new imaging pattern information of the disease to the literature. Key Words: 18F-FDG PET/CT, histiocytic sarcoma (Clin Nucl Med 2018;43: 65–67) Received for publication August 25, 2017; revision accepted November 3, 2017. From the Department of Nuclear Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People’s Republic of China. Conflicts of interest and sources of funding: none declared. Correspondence to: Yifan Zhang, MD, PhD, Department of Nuclear Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai 200025, People’s Republic of China. E-mail: zhang_yifan@126.com. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0363-9762/18/4301–0065 DOI: 10.1097/RLU.0000000000001908 REFERENCES 1. Ansari J, Naqash AR, Munker R, et al. Histiocytic sarcoma as a secondary malignancy: pathobiology, diagnosis, and treatment. Eur J Haematol. 2016; 97:9–16. 2. Pileri SA, Grogan TM, Harris NL, et al. Tumours of histiocytes and accessory dendritic cells: an immunohistochemical approach to classification from the International Lymphoma Study Group based on 61 cases. Histopathology. 2002;41:1–29. 3. 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Clinical Nuclear Medicine • Volume 43, Number 1, January 2018 Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. www.nuclearmed.com 65 Pan and Zhang Clinical Nuclear Medicine • Volume 43, Number 1, January 2018 FIGURE 1. A 52-year-old man, who had symptoms of intermittent head motor tics, expressive aphasia and right upper extremity weakness for 10 days, was referred to our hospital in May 2016. This patient had a previous history of allogeneic liver transplantation for HBV-related liver cirrhosis in 2005, and a descending-colon adenocarcinoma tumorectomy in 2007. A brain CT and MR revealed a space-occupying lesion with surrounding edema and central necrosis, located in the left frontal lobe. A subsequent 18F-FDG PET/CT scan showed annular 18F-FDG uptake in the brain lesion with SUVmax = 15.7 (A, arrowed in maximum intensity projection of PET; B, C and D, respectively arrowed in CT, PET and fused PET/CT). Simultaneously, a round lesion with partial 18F-FDG avidity (SUVmax = 7.5) was also detected in the left upper lobe of the lung (E, arrowed in maximum intensity projection of PET; F, G and H, respectively arrowed in CT, PET and fused PET/CT). Diagnosis of metastatic carcinoma was first suspected, given a history of colorectal carcinoma. Surgical resection of brain lesion was performed, and histopathological and immunohistochemical examinations finally showed a histiocytic sarcoma (HS). 66 www.nuclearmed.com © 2017 Wolters Kluwer Health, Inc. All rights reserved. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. Clinical Nuclear Medicine • Volume 43, Number 1, January 2018 Simultaneous Brain and Lung Histiocytic Sarcoma FIGURE 2. A needle biopsy of the lung lesion was initially performed 1 month after the brain surgery, which showed coagulative necrosis. Therefore, the patient underwent a series of follow-up chest CT examinations every 2–3 months from August 2016 to May 2017, which showed the lesion gradually enlarged with formation of a cavity inside (arrowed in all images; A, C, E, G and I, chest CT in mediastinal window; B, D, F, H and J, chest CT in pulmonary window; five lines of the images were respectively obtained in August, October, December 2016, and March, May 2017). In order to ascertain the lung lesion, a second needle biopsy was performed in May 2017, which again showed coagulative necrosis. As malignancy cannot be excluded, a bronchial mucosa biopsy of the left upper lobar bronchus was carried out, which finally showed HS as well. HS is a rare aggressive neoplasm, and is exceptionally rare in central nervous system.1 The diagnosis of HS depends on positive immunohistochemical markers of CD68/PG-M1, CD163 and lysozyme, and it is typically negative for B- and T-cell markers.1,2 Though imaging features of HS involving lymph nodes,3–5 pericardium6 and other tissues on 18F-FDG PET/CT have been previously described in a few case reports, it is still considered indistinguishable from other malignant tumors on imaging studies. This case of HS occurs in the brain and lung simultaneously, which is an additional PET/CT imaging finding of the disease. The needle biopsy of the lung lesion twice showed necrosis, likely due to the improper biopsy of the 18F-FDG-negative part. This highlights the significance of 18F-FDG PET/CT guided needle biopsy, particularly for lesions with heterogeneous 18F-FDG uptake.7,8 © 2017 Wolters Kluwer Health, Inc. All rights reserved. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. www.nuclearmed.com 67