- Human pathology

Home > E. Pathology by systems > Locomotory system > Bones > parosteal osteosarcoma

parosteal osteosarcoma

Tuesday 6 July 2004

Definition: Parosteal osteosarcomais a distinctive type of osteosarcoma that originates on the external surface of bone specifically in relation to the periostum or the immediate parosteal connective tissue or both.



Macroscopical synopsis

- hard, white, dense bone with frequent, small, peripheral, satellite nodules
- areas of fat or fibrous tissue interspersed within the lesion or in the clefts between satellites.
- areas of dedifferentiation appear soft and fleshy.
- amorphous, heavy trabeculae of disorganized bone admixed with dense, white, fibrous connective tissue.

Microscopical synospsis

- repetitive pattern of heavy trabeculae containing "Pagetoid" cement lines
- monotonous stroma of mature, spindle cells without cytologic atypia.
- nuclei of the stroma tend to be arranged parallel to each other and give the appearance of a "school of fish".
- areas of higher-grade osteosarcoma are rare and may be minute.
- mature, nonstress-oriented trabeculae are enmeshed in stroma of well-differentiated spindle cells.
- low cell-matrix ratio in the spindle cell stroma. The cells have a monotonous pattern resembling a school of fish swimming along a reef.
- long axis of the cells are parallel, there is no cellular atypia or mitoses and each cell looks exactly like the next.
- irregular, heavy cement lines in the neoplastic trabeculae and the low cell-to-matrix ratio in the stromal cells. low
- hyperchromatic spindle cells


- dedifferentiated parosteal osteosarcoma

See also

- opsteosarcomas