Malignant Bone‐Forming Neoplasm With NIPBL::BEND2 Fusion

• DOI: 10.1002/gcc.70015
• Publication Date: 2024-11-28T05:30:28Z
• Authors: Nooshin K. Dashti; George Matcuk; Abbas Agaimy; Carla Saoud; Cristina R. Anton...
• Keywords: Osteoid; Osteoblastoma; Pagetoid

ABSTRACT Conventional high‐grade osteosarcomas are characterized by aggressive radiologic features, cytologic pleomorphism, and complex genomics. However, rare examples of remain challenging due to unusual histology, such as sclerosing or osteoblastoma‐like which may require molecular confirmation their genetic alterations. We have encountered a case in 17‐year‐old man, who presented with third metatarsal sclerotic bone lesion, found incidentally the work‐up foot trauma. The initial imaging revealed lesion sclerotic/blastic features proximally lucent/lytic portion distally, findings interpreted consistent osteoblastoma. was managed intra‐lesionally curettings cryoablation; however, microscopic were non‐specific, showing bland osteoblastic proliferation embedded densely matrix. Subsequently, patient developed two rapid recurrences; first recurrence treated similarly despite its associated soft tissue extension radiographically, histologic remained non‐specific. 2nd showed large mass, destruction an open biopsy osteosarcoma lace‐like osteoid deposition, albeit uniform cytomorphology. subsequent below knee amputation compatible osteosarcoma, including solid growth epithelioid cells, vesicular nuclei scant cytoplasm, set meshwork There significant mitotic activity tumor necrosis. Tumor cells positive for SATB2. Further performed unexpected NIPBL::BEND2 fusion, has been previously reported cases phosphaturic mesenchymal (PMT). FGF23 (ISH) negative. By DNA methylation profiling, unsupervised clustering UMAP dimensionality reduction grouping not PMT group. received chemotherapy post‐amputation is alive without evidence disease, 10‐month follow‐up. report aggressive, overtly malignant acral bone‐forming tumor, harboring fusion. studies needed evaluate recurrent potential this fusion relationship PMT.