Achilles tendon xanthoma

Achilles tendon xanthomata are painless soft tissue masses occurring most commonly at the distal portion of the tendon and are usually bilateral and symmetrical.

Pathology

Characterized by localized accumulation of lipid-laden macrophages, inflammatory cells and giant cells secondary to cholesterol deposition in tissue.

Causes

Radiographic features

Plain radiograph
  • thickening of the Achilles tendon
  • no calcifications
  • other tendon or periarticular soft tissue nodularity may be present
  • often bilateral and symmetrical
Ultrasound
  • an AP thickness of the tendon >7 mm in males and >6 mm in females
  • tendon is more uniformly thickened as opposed to fusiform as seen in tendinopathy
  • loss of normal tendon appearance with multiple hypoechoic foci within the tendon but not fluid dark
  • often bilateral and symmetric
  • other ankle flexor and extensor tendons can be involved
MRI

Shows increased AP diameter of the distal tendon which is often uniform, not fusiform. Loss of the normal anterior concavity of the tendon can also be seen.

Signal characteristics include.

  • intermediate signal on T1- and T2-weighted sequences
  • higher T1- and T2-weighted signal compared to the normal tendon
  • T2 signal will not be 'fluid' bright as seen in partial-thickness tears
  • striated appearance in sagittal sequences due to interposition of xanthoma between normal tendon fibers
  • speckled appearance of the tendon in axial sequences

Other feautures

  • often bilateral and symmetric
  • other ankle flexor and extensor tendons can be involved

Differential diagnosis

Consider

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