Pathology · single question

A mucocele appears clinically blue in color. What is the BEST explanation for this appearance?

Accumulation of cyanotic blood in the cyst
The thin overlying mucosa causes selective light reflection (Tyndall effect), making it appear blue
Production of blue mucin by the extravasated glands
High vascularity of the overlying tissue

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Correct answer: B. The thin overlying mucosa causes selective light reflection (Tyndall effect), making it appear blue

A. Incorrect. Mucoceles contain saliva/mucin, not blood. Blood-filled lesions appear dark red or purple (hematoma).
B. Correct. A mucocele appears blue due to the Tyndall effect — short-wavelength (blue) light is scattered back by the thin overlying mucosa while longer wavelengths pass through. This optical phenomenon explains the blue translucent appearance of fluid-filled submucosal lesions.
C. Incorrect. Mucin is not blue. The blue color is an optical phenomenon of the overlying tissue, not a property of the cyst contents.
D. Incorrect. Vascularity produces a red or purple hue, not the characteristic blue of a mucocele.

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