MRI of soft-tissue masses: the relationship between lesion size, depth, and diagnosis

To identify the relationship between depth and size of soft-tissue mass lesions relative to histological diagnosis in a range of malignant neoplastic, benign neoplastic, and non-neoplastic conditions on magnetic resonance imaging (MRI).

The MRI findings of 571 consecutive patients referred to a supra-regional orthopaedic oncology unit with a suspected soft-tissue neoplasm were reviewed and included in the study. The patient age, histological diagnosis, lesion size, anatomical location, and lesion depth (superficial or deep to fascia) were recorded.

There were 288 males and 283 females (mean age 48 years, age range 2-92 years). The mean age was 54.1 years for malignant neoplastic lesions compared with 40.1 years for benign neoplastic and 45.4 years for non-neoplastic conditions. There was a significant age difference when malignant lesions were compared with benign neoplastic and non-neoplastic lesions (p<0.001). No significant relationship was present between lesion depth (480 deep, 91 superficial) and diagnosis (288 malignant neoplastic, 197 benign neoplastic and 86 non-neoplastic lesions). However, a significant relationship was identified between lesion size and diagnosis (p<0.001). Furthermore, a significant relationship was identified when lesion size greater than 5 cm, lesion depth, and diagnosis were analysed.

Current guidelines suggest the most important variables for assessing risk of malignancy in a soft-tissue lesion include size, depth in relation to the fascia, increasing size, and pain. The current study suggests that relationship to fascia is less important as a predictor of malignant potential in a patient cohort treated at a supra-regional centre. Significant risk factors include increasing patient age and lesion size greater than or equal to 5 cm.