Sonographic features of malignant lymph nodes
Lymphadenopathy is quite common, and it is many a time very difficult to differentiate malignant lymphadenopathy from reactive lymphadenopthy.
Several gray scale and colour doppler features favour malignancy in a lymph node.
Gray scale parameters that favour malignancy
- size: larger-more likely malignant
- shape: round, L/T <2
- heterogenous echotexture
- loss of central fatty hilum/thinning of hilum
- eccentric versus concentric thickening of cortex
- presence of microcalcifications
- necrosis: cystic/coagulative
- Ill defined capsular margins: invasion
Colour/power Doppler features that favour malignancy
- peripheral/mixed peripheral: central blood vessels
- high resistance waveform
- R.I. >0.8, P.I. >1.5
- abberent vessels: displaced parent vessels, subcapsular vasculature, unperfused areas, non tapering vessels
The increase in resistivity in a malignant lymph node is attributed to increased cellularity within an infiltrated lymph node. However, malignant lymph nodes with necrotic change may show low resistance flow due to loss in the cellularity following necrosis & this needs to be kept in mind while interpreting this sign.
When used in combination the above signs can help differentiate a malignant lymphadenopathy from reactive lymphadenopathy.