String sign (bones)

Last revised by Matt A. Morgan on 19 Jan 2021

The string sign of parosteal osteosarcoma refers to the plain radiographic/CT appearance of a radiolucent cleavage plane between portions of the tumor and cortex of the affected bone. The tumor stalk becomes more broad-based with time, obliterating the string sign in later stages.

The string sign can also be seen in myositis ossificans.

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