Yin-yang sign (solitary fibrous tumor)
The yin-yang sign is a radiologic appearance described in solitary fibrous tumor of the dura on MR.
On T2-weighted images, these tumors have two separate solid components, one that is hyperintense and one that is iso- to hypointense relative to brain parenchyma. Histologically, the former represents more hypercellular areas, while the latter represents more conspicuous collagenous stroma. The sign has also been described as a "patchy" or "black-and-white mixed" appearance. While some authors consider the appearance characteristic of solitary fibrous tumor , other authors have found it infrequently .
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