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Abstract：
BACKGROUND Phosphaturic mesenchymal tumor (PMT) is an extremely rare mesenchymal neoplasm that is commonly seen in bone and soft tissue. It is associated with a paraneoplastic syndrome, oncogenic osteomalacia, due to tumor-induced urinary phosphate wasting. It is demonstrated to be predominantly mediated by fibroblast growth factor 23 (FGF23)/fibroblast growth factor receptor 1 (FGFR1) axis. Clinically, PMT usually presents as a solitary lesion in the bone. The diagnosis of PMT is challenging due to its non-specific clinical manifestation, radiologic findings, and morphological features. CASE REPORT We report the case of a 50-year-old man presenting with multiple lytic bone lesions and associated pathologic fracture of the right femur, clinically suspicious for multiple myeloma or other metastatic malignant process. Resection from the right femur showed a hypercellular lesion composed of oval-to-spindled cells infiltrating the native trabecular bone with admixed multinucleated giant cells. Immunohistochemical (IHC) staining and in situ hybridization (ISH) demonstrated the tumor cells were positive for SATB2, ERG, FGFR1, and FGF23 ISH. DNA and RNA next-generation sequencing showed marked increases in mRNA levels of FGF23 and FGFR1. The constellation of clinicoradiologic, histomorphologic, IHC, and molecular findings supported a diagnosis of primary benign PMT. CONCLUSIONS This case report discusses a patient with PMT presenting with multifocal lesions due to tumor-induced osteomalacia at initial presentation. We hope that this report will increase the awareness of clinician and pathologists of PMT as a differential diagnosis in patients presenting with multifocal lytic bone lesions. In turn, this will prevent misdiagnosis and overtreatment of a typically benign process.
摘要：
背景技术磷间充质肿瘤(PMT)是一种极其罕见的间充质肿瘤,常见于骨和软组织中。它与副肿瘤综合征有关，致癌骨软化症，由于肿瘤引起的尿磷酸盐消耗。已证明主要由成纤维细胞生长因子23（FGF23）/成纤维细胞生长因子受体1（FGFR1）轴介导。临床上,PMT通常表现为骨骼中的孤立性病变。由于PMT的非特异性临床表现，其诊断具有挑战性。放射学发现，和形态特征。案例报告我们报告了一例50岁的男性，表现为多发性溶解性骨病变和相关的右股骨病理性骨折，临床怀疑多发性骨髓瘤或其他转移性恶性过程。从右股骨切除显示出高细胞病变，由椭圆形至纺锤形的细胞浸润天然小梁骨，并混合了多核巨细胞。免疫组化(IHC)染色和原位杂交(ISH)显示肿瘤细胞SATB2、ERG阳性,FGFR1和FGF23ISH。DNA和RNA下一代测序显示FGF23和FGFR1的mRNA水平显著增加。临床放射学的星座，组织形态学,IHC,分子研究结果支持原发性良性PMT的诊断。结论本病例报告讨论了一名PMT患者在最初表现时因肿瘤诱导的骨软化症而出现多灶性病变。我们希望该报告将提高临床医生和病理学家对PMT的认识，以作为多灶性溶解性骨病变患者的鉴别诊断。反过来,这将防止误诊和过度治疗一个典型的良性过程。
