Age / Sex : 48 / M

Chief complaint :

Left heel mass (1yr), construction worker

What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : Ji Na Kim, Chungnam National University Hospital

Discussion

Answer:  

Clear Cell Sarcoma

Findings:

Lateral radiograph of foot shows a hell mass at the heel with mild bone erosion of the calcaneal tuberosity

Non-contrast sagittal CT image of foot shows isodensity soft tissue mass of the heel and no internal calcification,

Sagittal T1- and fat saturated T2- weighted images reveal a large mass involving subcutaneous tissue and Achilles tendon. The mass has slightly higher signal intensity compared with foot muscle on T1 weighted images and intermediate to high signal intensity on T2 weighted images. Erosion with signal change of the adjacent calcaneal tuberosity is also seen.

Differential Diagnosis:

Synovial sarcoma

UPS

Discussion:

Melanoma of soft part, but melanin is microscopic.

Young adult (20 to 40 yrs) with predilection for foot and ankle (43% of cases).

Theoretic effects of melanin (slightly increased signal intensity on T1-weighted images compared with muscle and low signal on T2-weighted images) can be shown, but not prominent because of the minute amount of melanin.

Poor prognosis.

References:

1. Beuckeleer et al. MR imaging of clear cell sarcoma (malignant melanoma of the soft parts): a multicenter correlative MRI-pathology study of 21 cases and literature review. Skeletal Radiology 2000;29:187-195


2. Imaging of Soft Tissue Tumors. 3^rd ed. Kransdorf et al. p435