Apparent diffusion coefficient correlates with different histopathological features in several intrahepatic tumors

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OBJECTIVES: To investigate associations between apparent diffusion coefficient (ADC) and cell count, Ki 67, tumor-stroma ratio (TSR), and tumoral lymphocytes in different hepatic malignancies. METHODS: We identified 149 cases with performed liver biopsies: hepatocellular cancer (HCC, n = 53), intrahepatic cholangiocarcinoma (iCC, n = 29), metastases of colorectal cancer (CRC, n = 24), metastases of breast cancer (BC, n = 28), and metastases of pancreatic cancer (PC, n = 15). MRI was performed on a 1.5-T scanner with an axial echo-planar sequence. MRI was done before biopsy. Biopsy images of target lesions were selected. The cylindrical region of interest was placed on the ADC map of target lesions in accordance with the needle position on the biopsy images. Mean ADC values were estimated. TSR, cell counts, proliferation index Ki 67, and number of tumor-infiltrating lymphocytes were estimated. Spearman's rank correlation coefficients and intraclass correlation coefficients were calculated. RESULTS: Inter-reader agreement was excellent regarding the ADC measurements. In HCC, ADC correlated with cell count (r = - 0.68, p < 0.001) and with TSR (r = 0.31, p = 0.024). In iCC, ADC correlated with TSR (r = 0.60, p < 0.001) and with cell count (r = - 0.54, p = 0.002). In CRC metastases, ADC correlated with cell count (r = - 0.54 p = 0.006) and with Ki 67 (r = - 0.46, p = 0.024). In BC liver metastases, ADC correlated with TSR (r = 0.55, p < 0.002) and with Ki 67 (r = - 0.51, p = 0.006). In PC metastases, no significant correlations were found. CONCLUSIONS: ADC correlated with tumor cellularity in HCC, iCC, and CRC liver metastases. ADC reflects TSR in BC liver metastases, HCC, and iCC. ADC cannot reflect intratumoral lymphocytes. CLINICAL RELEVANCE STATEMENT: The present study shows that the apparent diffusion coefficient can be used as a surrogate imaging marker for different histopathological features in several malignant hepatic lesions. KEY POINTS: • ADC reflects different histopathological features in several hepatic tumors. • ADC correlates with tumor cellularity in HCC, iCC, and CRC metastases. • ADC strongly correlates with tumor-stroma ratio in BC metastases and iCC.

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