A 20-year- old male presented with a painless, hard subcutaneous mass in the popliteal fossa. He stated that the mass had been present for several years and did not change in size. Two words, "painless" and "non-growing" (or very slow growing), suggest that the lesion described here is probably benign.

What would be the possible diagnosis looking at the radiograph and pathological findings? *This case is from the Docplexus Editorial Team and is meant for educative purpose only.