Terms, definitions and measurements to describe sonographic features of lymph nodes: consensus opinion from the Valvular International Tumor Analysis (VITA) group

Terms, definitions and measurements to describe sonographic features of lymph nodes: consensus opinion from the Valvular International Tumor Analysis (VITA) group

REVIEWED BY | Jennifer Alphonse PhD ASA SIG: Obstetrics

REFERENCE | Authors: D Fischerova, G Garganese, H Reina, SM Fragomeni, D Cibula, O Nanka, T Rettenbacher, AC Testa, E Epstein, I Guiggi, F Frühauf, G Manego, G Scambia and l Valentin Journal: Ultrasound in Obstetrics and Gynecology Open Access: Yes

WHY THE STUDY WAS PERFORMED

As no international consensus on the ultrasound assessment of lymph nodes in any anatomical location existed, in 2016 the Valvular International Tumor Analysis (VITA) group was formed with the aim to provide inguinal lymph nodes description, measurement technique, terminology and examination technique in women with vulvar cancer. The nomenclature suggested could also be applied to lymph nodes in other superficial areas of the body, or deep lymph nodes where patient habitus and ultrasound technology permit high resolution assessment. It should be noted that an agreement between ultrasound features and histopathological diagnosis has not yet been established; however, the group hopes that this consensus statement will encourage prospective research for the identification of ultrasound features typical of lymph node metastases and a standardised approach to ultrasound examination, description and reporting.

HOW THE STUDY WAS PERFORMED

Inguinal lymph nodes should be examined utilising a high frequency linear array transducer (7.5–14 MHz). Systematic assessment of the femoral triangle is essential by sonographers with anatomical knowledge of the region. The paper describes the ultrasound landmarks that designate the boundaries of the femoral triangle, which include the inguinal ligament, adductor longus muscle and the sartorius muscle, detailed in Appendix S3 with tips and tricks in Appendix S4.

The patient is positioned supine with legs extended and apart. The ultrasound assessment begins at the apex of the femoral triangle with the transducer in transverse, moving cranially and slowly. Gentle pressure is recommended as compression of the femoral vein will affect orientation. Assessment continues until the inguinal ligament is reached. This assessment establishes the region of interest following with the assessment of the lymph nodes performed in both transverse and longitudinal planes. High magnification and resolution are maintained throughout scanning and should include surrounding perinodal tissues to assess grouping.

Lymph nodes are examined utilising both quantitative (measurement) and qualitative (description) parameters. A normal lymph node has regular contours, is oval in shape, and when measured in two planes has a long-axis-to-short-axis ratio (L/S ratio) > 2. Other measurements include cortical-thickness-to-medullar-thickness ratio (C/M) and maximumcortical-thickness-to-minimum-cortical-thickness ratio (Cmax/Cmin), which are both described in detail.

Qualitatively, dominant characteristics should be the focus of the assessment rather than the minute changes. The medulla is central and hyperechogenic while the cortex is continuous and hypoechoic with a thin echogenic capsule. There is an echogenic hilum interrupting the cortex which contains a blood vessel that passes from the adjacent perinodal tissue to the medulla. On colour Doppler imaging (CDI) branches may be seen within the medullar.

Other lymph node classifications covered by this article include reactive lymph nodes, postreactive lymph nodes and metastatic lymph nodes, all with detailed descriptions, schematic diagrams and ultrasound images with both 2D and CDI.

“In gynaecologic oncology centers with available ultrasound expertise, ultrasound alone is the method of choice for preoperative assessment of inguinal lymph nodes, [however] the lack of standardized ultrasound nomenclature to describe lymph nodes makes it difficult to compare results from different ultrasound studies and to find reliable ultrasound features for distinguishing non-infiltrated lymph nodes from lymph nodes infiltrated by cancer.”

WHAT THE STUDY FOUND

As there are no internationally accepted standardised terms to describe the ultrasound appearance of lymph nodes regardless of the anatomical position, it is difficult to compare the results from different ultrasound studies. As terms are non-standardised, the ultrasound characteristics of lymph nodes infiltrated by cancer or lymphoma are unable to be compared ultrasonically from metastatic lymph nodes from primary cancer. Further, the normal appearance of head and neck, axillary and inguinal lymph nodes differ ultrasonically.

Standardised examination techniques and terminology are needed and correlation with histopathological diagnosis is essential.

RELEVANCE TO CLINICAL PRACTICE

This is not a definitive document, and based on the quality of future research, it will continually be adjusted. However, as lymph node assessment and ultrasound description in clinical practice vary greatly, this paper may assist in a more standardised approach to ultrasound assessment, description and reporting of lymph nodes.