TY - JOUR T1 - PET/CT Findings: Langerhans Cell Sarcoma Arising from Langerhans Cell Histiocytosis JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 2031 LP - 2031 VL - 62 IS - supplement 1 AU - Shuihua Zhang AU - Pei Han AU - Chuyun Xiang AU - Ping Chen Y1 - 2021/05/01 UR - http://jnm.snmjournals.org/content/62/supplement_1/2031.abstract N2 - 2031Objectives: This paper aims to highlight the indications of positron emission tomography (PET)/computed tomography (CT) imaging in Langerhans cell sarcoma (LCS), evaluate the clinicopathologic feature of LCS, and reveal the follow-up value of PET/CT in patients with LCS. Abstract: The LCS is a rare Langerhans cell-derived malignancy. Langerhans cell hyperplasia is classified into two main subgroups: Langerhans cell histiocytosis (LCH) and LCS. LCS is considered as a high-grade malignant variant of LCH, which may be primary or may develop from LCH. In this study, a 52-year-old male patient initially presented with cutaneous lesions in the left lower extremities, and a pathologic biopsy of the lesion was performed for LCH. For the first time, PET/CT examination demonstrated high-grade activity of skin nodules on the left lower extremities alone. After treatment, the skin lesions of the lower limbs disappeared. However, a mass in the left lower neck was found one year later, and the second systemic PET/CT study showed distal bilateral peripheral lung metastasis, multiple enlarged lymphadenopathies throughout the body, and significant increase of FDG activity of lesions. Moreover, the histopathology of lymph node biopsy revealed significant malignant cytologic features as well as CD1a- and S-100-positive cells using immunohistochemistry staining, typical for LCS. LCS is usually characterized by cellular atypia and clinical invasiveness, which can involve multiple organs in the disease progression. As LCS is a high-grade malignant tumor with poor prognosis, strict histological analysis and thorough imaging examination are necessary for accurate tumor diagnosis. Thus, PET/CT has high application value in the diagnosis, follow-up, and efficacy evaluation of LCH and LCS diseases. Consequently, the LCH possibility of malignant transformation into LCS should be considered, especially when LCH occurs in middle-aged or elderly people and lesion progress or distant metastasis occurs during follow-up. Supporting data Figure 1. Systemic PET/CT examination showed multiple hypermetabolic lesions (A, MIP of PET). Multiple swollen lymphadenopathies (B, C, D, E) and multiple metastatic tumors in both distal bilateral peripheral lungs (F, G) showed remarkable FDG activity. ER -