Genetic aberration and pathological diagnosis in bone and soft-tissue tumors

Bone and soft-tissue sarcomas comprise a rare, complex, and heterogeneous group of tumors for which it is difficult for even experienced pathologists to provide a conclusive diagnosis. The number of diagnoses made using genetic analysis has increased since the detection of fusion genes in several soft-tissue tumors in the 1990s. Moreover, other specific genetic aberrations have been reported in various bone and soft-tissue tumors. In addition, molecular therapeutic targets have been sought in advanced cases of soft-tissue and bone tumors similar to other organ malignancies. To enable the pathological diagnosis of bone and soft-tissue tumors, it is necessary to combine histological diagnosis with immunohistochemistry and gene analysis findings including fusion gene or other genetic aberrations. In this review, we describe the fusion genes recently reported in bone and soft-tissue tumors such as solitary fibrous tumor, aneurysmal bone cyst, nodular fasciitis, CIC-DUX4 fusion gene-positive small round cell tumors, or BCOR-CCNB3-positive sarcoma as well as other genetic aberrations in dedifferentiated liposarcoma, malignant rhabdoid tumor, cartilaginous tumor, Langerhans cell histiocytosis chondroblastoma, or giant cell tumor of the bone. We also demonstrate their association with pathological diagnosis.