LN-RADS 1 normal LN
No enlargement (recommended max SAD up to 6-7mm), oval shape (L/S-ratio > 2), regular cortex max thickness ≤3mm, cortex echogenicity similar or higher to the background fatty tissue, smooth margins, no others changes in architecture (no calcifications, no fluid collections, no necrosis, no FCT), no pathological peripheral or chaotic vascularization

LN-RADS 2 steatotic LN
LNs enlarged in one or both axes, cortex regular, max thickness ≤3mm,  hilum  hyperechoic (steatotic) with no size limits, no other changes in architecture (no calcifications, no fluid collections, no necrosis, no FCT), no pathological peripheral or chaotic vascularization)

LN-RADS 3 reactive LN
Probably due to inflammatory process or vaccination. Dominant feature: regular, thickened cortex >3mm, enlargement in one or two axes, preserved oval shape (L/S-ratio > 2), preserved medulla, no others changes in architecture (no calcifications, no fluid collections, no necrosis, no FCT), cortex echogenicity similar or moderately lower to the background fatty tissue, well defined margins, no pathologic peripheral or chaotic vascularization, no oncological, hematological history, no laboratory oncological abnormalities

LN-RADS 4 suspicious LN
4a low, 4b high probability of malignancy. This group is dedicated to LNs that morphologically don’t match to group 1, 2, 3, 5 or have additional radiological or clinical factors increasing probability of malignancy in LNs categorized as LN-RADS 3 i.e. high or increasing laboratory markers (i.e. PSA for inguinal LNs), active neoplasm in the region (i.e. breast cancer for axillary LNs), another metastatic or systemic LNs in the region, clinical symptoms suggesting oncological or systemic hematological disease. The main rule of selecting LNs to group 4 is that “better check than miss” .

LN-RADS 4a low suspicious for malignancy – size may be normal in SAD and LAD, cortex  with thickenning ≤4mm,  moderate  irregularity especially local. In assumption all LN 4a should be verified in biopsy or PET,  if it is not possible they should be treated as suspected and malignant.    

LN-RADS 4b high suspicious of malignancy – size may be normal in SAD and LAD, cortex  thickening >4mm and irregularity,  especially FCT, or no hilum, shape more round than oval (L/S-ratio≤2), hypoechogenicity to background fatty tissue especially “black hole sign”, micro-calcifications, fluid collections, necrosis,  abnormal peripheral or chaotic vascularization architecture, ill-defined blurred margin

LN-RADS 5 malignant LN
Enlargement in SAD and one or more malignancy features: lack of hilum, hypoechogenicity to the background fatty tissue or “black hole sign”, evident cortex irregularity /FCT,”  shape more round than oval (L/S-ratio≤2), micro-calcifications, fluid collections, necrosis, abnormal peripheral or chaotic vascularization architecture, ill defined, blurred borders or sign of extracapsular infiltration.

If strong radiological and clinical features of malignancy are present,  enlargement is not neccessary to classification to LN-RADS 5