tadpole sign

(1) A term referring to the appearance of early embryos when examined by ultrasonography
(2) A comma-shaped ultrasound ‘shadow’ seen under a tumour, which is of lesser density directly beneath the center of a mass than at the edges; ‘tadpoles’ appear in malignant masses and have ragged margins, due to necrotic tissue, which is a poor conductor of ultrasound waves.
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tadpole sign

Imaging A comma-shaped ultrasound 'shadow' seen under a tumor, which is of lesser density directly beneath the center of a mass than at the edges; 'tadpoles' appear in malignant masses and have ragged margins, due to necrotic tissue, which is a poor conductor of US waves. See Ultrasonography. Cf Tennis racquet sign.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.