Soft tissue mass resembling myxochondroid metaplasia in Achilles tendon

The Achilles tendon is the strongest and largest tendon in the human body, composed of the distal confluence of the gastrocnemius and soleus muscles and may also include the plantaris longus tendons. Despite its tremendous strength, it is frequently injured. Soft tissue tumors or tumor-like conditions of Achilles tendon are much less common in comparison to traumatic and infectious/inflammatory lesions. These include giant cell tumor of the tendon sheath, pigmented villonodular synovitis, xanthomas, hematomas, and tophaceous gout. We present a case of a myxochondroid mass arising from the Achilles tendon in a 17-year-old female softball player detected after a minor trauma. According to our knowledge, this is the first case reported in the literature detailing the radiological findings and histopathological diagnosis of a myxochondroid mass arising from a tendon.