Comparison of ADC values in different malignancies of the skeletal musculature: a multicentric analysis

Diffusion-weighted imaging (DWI) provides essential information regarding tumor composition, such as cellularity and/or perfusion. DWI is helpful in distinguishing between malignant and benign lesions. Malignant intramuscular/soft tissue lesions consist of a wide spectrum of tumors that have different cell counts and matrix. It is presumed that these different tumors have different DWI findings and have different apparent diffusion coefficient (ADC) values. The aim of this study was to analyze DWI findings of different intramuscular malignancies in a multicentric study by using a standardized DWI protocol, and to compare the ADC values acquired.

The data banks of four radiology departments were screened retrospectively for malignant intramuscular tumors. Only lesions that were investigated by MRI (with a 1.5-T scanner) using DWI (multishot EPI sequence with b values of 0 and 1,000 s/mm(2)) were included in the study. Overall, 51 patients (28 women, 23 men; mean age 58.8 ± 16.1 years) with 57 different malignant intramuscular lesions were collected. In every case apparent diffusion constant (ADC) maps were calculated. In 14 patients muscle lymphoma, 11 patients intramuscular metastases from different primary tumors, and in 26 cases several muscle sarcomas were identified.

The mean ADC value of the estimated lesions was 1.24 ± 0.53 × 10(-3) mm(2)s(-1), median value, 1.11 × 10(-3) mm(2)s(-1), range, 0.54-2.9 × 10(-3) mm(2)s(-1). The mean ADC value in muscle metastases was 1.28 ± 0.24 × 10(-3) mm(2)s(-1), in muscle lymphoma 0.76 ± 0.14 × 10(-3) mm(2)s(-1), and in muscle sarcomas 1.82 ± 0.63 × 10(-3) mm(2)s(-1). Muscle lymphoma showed statistically significant lower ADC values in comparison to muscle metastases (p = 0.01) and muscle sarcoma (p = 0.001). There was no significant differences between ADC values in muscle metastases and sarcomas (p = 0.48). ADC values in muscle lymphoma were homogeneous with less inter-patient variability and were within a relatively close range. Muscle sarcomas had a broad range of ADC values.

Intramuscular malignant lesions had different ADC values on DWI. 22.8% of the tumors analyzed had low ADC values, 26.3% moderate, and 50.9% high ADC values. Muscle lymphoma had statistically significantly lower ADC values in comparison to muscle metastases and sarcomas. Muscle sarcomas presented with a broad range of ADC values.