Fig. 4

Magnetic resonance images of the patient’s left foot. a Sagittal T1-weighted turbo spin echo (TSE) image. b Sagittal T1-weighted TSE contrast-enhanced image with Ga-DTPA fat -suppressed. c Coronal proton density (PD)-weighted TSE fat-suppressed image. d Transverse T1-weighted TSE contrast-enhanced image with Ga-DTPA fat-suppression. Another well-enhanced mass was identified beside the flexor hallucis longus tendon at the level of the talonavicular joint (arrows). Considering that the patient was diagnosed with melanoma, these appearances were in favor of metastases from melanoma according to a radiologist. However, the differential diagnosis was pigmented villous nodular synovitis