The diagnostic accuracy of DWI and ADC in predicting axillary lymph nodes status
DWI - Diffusion weighted imaging (DWI) is a non-contrast MRI technique that can provide unique information about intercellular water motion (Figure 6).
Every change in the movement of water protons produces a variation of signal intensity on DW images and,
as a consequence,
apparent diffusion coefficient (ADC) maps,
being sensitive to certain parameters such as cell organization,
cell density,
microstructure and microcirculation.
Initial reports demonstrated that DW imaging may be a valuable tool for identifying and characterizing breast lesions and monitoring treatment response.
Because of its high sensitivity,
DWI might find its utility also in detecting malignant axillary lymph nodes.
ADC - is calculated automatically and then displayed as a parametric map that reflects the degree of diffusion of water molecules through different tissues.
Then,
by use of a dedicated workstation,
ADC measurements are recorded for a given region by drawing regions of interest (ROIs) on the ADC map.
The mean ADC of metastatic lymph nodes shows up to be lower than that of benign nodes,
as a result of more condensed cells and thus restricted water molecules diffusion (Figure 7).
Case 1: Invasive lobular carcinoma in 70-year-old woman with palpable left breast nodule.
US-guided FNA confirmed the presence of metastatic disease in the left axilla (Figure 8).
Case 2: 37-year-old woman with history of previous bilateral breast reduction surgery (1983) and voluminous palpable mass of the left breast.
Core needle biopsy was performed,
yielding histology consistent with intermediate grade ductal carcinoma.
(Figure 9).
Case 3: 69-year-old woman at high familial risk for breast cancer with palpable nodule of the left breast.
Core needle biopsy was performed,
yielding histology consistent with invasive ductal carcinoma.
The patient underwent breast DCE MR examination for staging malignancy (Figure 10).
Case 4: Invasive ductal carcinoma of the right breast in 65-year-old woman with paplable nodule of the right breast (Figure 11).
Case 5: Invasive lobular carcinoma in 70-year-old woman with palpable left breast nodule (Figure 12).
Case 6: 48-year-old patient with newly diagnosed right breast cancer - grade II invasive mucinous carcinoma (Figure 13).
THE LITERATURE REVIEW
There are few research articles published in the medical literature in English,
which confirmed the usefulness of DWI in differentiating metastatic from non-metastatic lymph nodes,
reporting a statistically significant difference (P < 0.01 or less) between the mean ADC value measured in the former and in the latter condition (Figure 14 - Table 3).
Adopting a threshold value of 1.09x10‾³mm²/s DWI resulted in 94.7% sensitivity,
91.7% specificity,
and 93.0% accuracy in the identification of metastasis in the series of lymph nodes (Figure 14 - Table 4).
On the other hand,
Schipper et al.
(Diagnostic Perfomance of Dedicated Axillary T2- and Diffusion-weighted MR Imaging for Nodal Staging in Breast Cancer.
Radiology Dec 2014,
15:141167) showed in their study that the quantitative measurement of the mean ADC of each lymph node has low diagnostic performance (AUC,
0.54-0.58),
with no statistically significant difference in mean ADC between lymph nodes with and those without macrometastasis.
The diagnostic performance of dedicated axillary T2- and Diffusion-weighted MR imaging for nodal staging in patients with breast cancer is insufficient to replace sentinel lymph node biopsy in clinical practice.