Osteosarcoma occurring outside of bone tissue is a rare soft tissue tumor.

bubble_chart Pathological Changes

1. Gross examination reveals a well-demarcated tumor from the surrounding tissue, with a granular cut surface appearing grayish-white or pale yellow, and small hemorrhagic foci can be observed.

2. Microscopically, it shows no significant difference from primary osteosarcoma of bone, displaying atypical osteoblasts, spindle-shaped cells, multinucleated giant cells, osteoid matrix, bone, and atypical chondrocytes.

bubble_chart Clinical Manifestations

Unlike osteosarcoma originating in bone, extraskeletal osteosarcoma is more common in adults over 40 years old and often occurs in the thighs and buttocks.

bubble_chart Treatment Measures

The literature reports that although most patients undergo various treatments, they generally die from metastases within 2 to 3 years after diagnosis. Hematogenous metastasis is common, and some patients also experience lymph node metastasis.

bubble_chart Differentiation

The differential diagnosis needs to distinguish from parosteal osteosarcoma: On X-ray, lesions where the tumor is continuous with the periosteum can be observed. Histologically, lesions in the bone cortex can be seen. Periosteal osteosarcoma: On X-ray, lesions in the bone cortex can be observed, with no lesions in the medullary cavity.