What causes Ring sign in bone tumors on radiographs, CT, or MRI?
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Answer:
The Ring sign is caused by osteochondromyxoma, a rare bone tumor often associated with Carney complex (CNC), a genetic syndrome. Osteochondromyxoma presents as a lesion with a characteristic radiological appearance showing a well-defined ring-like margin. This sign aids in the diagnosis of this tumor subtype. Note that the term “ring sign” is also used for several unrelated findings in radiology (e.g., the cerebral ring-enhancing lesion of abscess/metastasis, the ring sign of a ureteral stone on urography, and the tendon ring sign in the ankle) — these are distinct entities from the bone-tumor ring sign described here.
Why is it called so?
It is named the Ring sign because the lesion demonstrates a distinct ring-shaped margin on imaging studies, appearing as a hyperdense border or ring around the lesion on X-ray and CT, and as a low signal intensity ring on both T1- and T2-weighted MRI sequences.
Pathophysiology
The ring appearance results from sclerotic bone or dense fibrous tissue formation at the periphery of the osteochondromyxoma lesion. This dense rim contrasts with the central tumor tissue on imaging, producing the characteristic ring-shaped sign.
Alternative names: None specifically reported for this ring sign in osteochondromyxoma.
Other associated named signs: Irregular ring sign and bubble sign have been described in osteochondromyxoma imaging but are distinct from the classic Ring sign.
References
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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