[Primary extraskeletal osteosarcoma: a clinicopathological study of ten cases].

Abstract

Objective: To investigate the clinicopathologic features, differential diagnosis, immunohistochemical profiles and molecular characteristics of primary extraskeletal osteosarcoma (ESOS). Methods: Ten cases of ESOS diagnosed and treated in Fujian Provincial Hospital, Fuzhou, China from January 2003 to January 2019 were collected and subjected to immunohistochemical staining and molecular analyses. The patients were followed up by telephone interview. Relative literature was also reviewed to assess the characteristics of this tumor. Results: The ten cases occurred in 3 women and 7 men, aged from 36 to 85 years (median, 60 years). The sizes of these tumors ranged from 5.5 to 17.5 cm (median, 11.0 cm). Histologically, at low magnification, the tumors were nodular, leafy and lobulated. They were composed of spindle cells, neoplastic osteoid cells, and cartilage tissues, with unequally-proportional mixture of these components. The three components intermingled with each other. Immunohistochemistry profiling showed that the tumor cells were positive for SATB2 (9/9), while α-SMA (4/10) and EMA (1/10) stains were focally positive. Ki-67 proliferation index was 10%‒50%. Desmin, CD68, S-100 protein, SOX10, HMB45, CD117, DOG1, CD34, CKpan, GATA3 and PAX8 stains were negative. MDM2/CDK4 gene amplification signals were not detected in the 6 cases (0/6), which were subjected to the FISH. The SSX18 break-apart signal and the C-KIT and PDGFR-α mutations were not detected (0/5 and 0/3, respectively). Conclusions: Primary ESOS is an extra-osseous osteogenic tumor. The diagnosis is mainly dependent on clinical, radiological and pathological characteristics. Immunohistochemistry and molecular profiling are helpful for making the correct diagnosis.