The role of the ADC value in the characterisation of renal carcinoma by diffusion-weighted MRI

Abstract

The purpose of this study is to evaluate the role of diffusion-weighted imaging (DWI) in combination with T(1) and T(2) weighted MRI for the characterisation of renal carcinoma. The institutional review board approved the study protocols and waived informed consent from all of the patients. 47 patients (32 male and 15 female; age range, 21-85 years; median age, 65 years) who had suspected renal lesions on abdominal CT underwent MRI for further evaluation and characterisation of the lesions from April 2005 to August 2007 in our university hospital. A region of interest was drawn around the tumour area on apparent diffusion coefficient (ADC) maps. Final diagnosis was confirmed by histological examination of surgical specimens from all patients. The ADC value was significantly higher in renal cell carcinoma (RCC) than in transitional cell carcinoma (2.71+/-2.35 x 10(-3) mm(2) s(-1) vs 1.61+/-0.80 x 10(-3) mm(2) s(-1); p = 0.022). While analysing the histological subtypes of RCC, a significant difference in ADC values between clear cell carcinoma and non-clear cell carcinoma was found (1.59+/-0.55 x 10(-3) mm(2) s(-1) vs 6.72+/-1.85 x 10(-3) mm(2) s(-1); p = 0.0004). Similarly, ADC values of RCC revealed a significant difference between positive and negative metastatic lesions (1.06+/-0.38 x 10(-3) mm(2) s(-1) vs 3.02+/-2.44 x 10(-3) mm(2) s(-1); p = 0.0004), whereas intensity on T(1) and T(2) weighted imaging did not reach statistical significance. In conclusion, DWI has clinical value in the characterisation of renal carcinomas and could be applied in clinical practice for their management.

Figure 1

Transverse MR images of a 65-year-old woman with transitional cell carcinoma of the left kidney. (a) T₂ weighted image showing a low-signal-intensity mass of the left kidney (arrow). (b) On DWI, the tumour showed very high signal intensity (arrow). (c) The apparent diffusion coefficient map shows the low ADC value (0.71 × 10⁻³ mm² s) of the tumour (arrow). (d) Haematoxylin and eosin (H&E) staining confirmed the histological diagnosis of TCC. Densely packed solid tumour cells with hypercellularity were seen (original magnification, ×100).

Figure 2

Transverse MR images of a 53-year-old man with clear cell carcinoma of the right kidney. (a) T₂ weighted image showing a slightly high-signal-intensity mass lesion (arrow). (b) Transverse diffusion-weighted MR image showing slightly high signal intensity (arrow). (c) The apparent diffusion coefficient map shows the low ADC value (2.11 × 10⁻³ mm² s) of the tumour (arrow). (d) Haematoxylin and eosin (H&E) staining of clear cell carcinoma shows large tumour cells with small round nuclei and plenty of clear cytoplasm. Note the intercellular space is very narrow compared with that in Figure 4d (original magnification, ×200).

Figure 3

Apparent diffusion coefficient (ADC) values of transitional cell carcinoma (TCC) and renal cell carcinoma (RCC). ADC values were significantly higher in RCC than in TCC (p = 0.022).

Figure 4

Transverse MR images of a 54-year-old man with papillary renal cell carcinoma of the left kidney. (a) T₂ weighted image showing a high-signal-intensity mass lesion (arrow). (b) Transverse diffusion-weighted MR image showing high signal intensity (arrow). (c) The apparent diffusion coefficient map shows the low ADC value (2.51 × 10⁻³ mm² s) of the tumour. (d) Haematoxylin and eosin (H&E) staining confirmed the histological diagnosis of papillary carcinoma of renal tumour. A distinct papillary structure is formed by single layers of tumour cells arranged around vascular stroma with wide intercellular spaces (original magnification, ×100).

Figure 5

Relationship between the apparent diffusion coefficient (ADC) values for clear cell carcinoma (ccc) and non-clear cell carcinoma. A significant difference was noted in the ADC value between clear cell carcinoma and non-clear cell carcinoma (p = 0.0004).

Figure 6

Comparison of distant metastasis of renal cell carcinoma in 32 patients with the apparent diffusion coefficient (ADC) value and T₁ or T₂ weighted scores. (a) The ADC value was significantly associated with the existence of metastasis (p = 0.0004). No association of distant metastasis (meta) was observed with (b) T₁ weighted scores or (c) T₂ weighted scores.