Acral Fibromyxoma
Background
Acral fibromyxoma is a rare benign neoplasm of fibroblastic origin. By definition, it's restricted to peripheral (acral) sites and is most often found the periungual region of the fingers and toes. They are usually painless (60% of the time) and can cause nail deformities and even remodeling of the underlying bone.Imaging
Conventional radiographs may demonstrate soft tissue swelling and chronic pressure erosion/remodeling of the underlying bone. Calcifications have not been described.Ultrasound appearance ranges from homogenously hypoechoic to low-level internal echoes. Color Doppler features range from avascular to variable vascularity with areas of necrosis.
on MRI, the lesions have a cystic appearance with thin internal septations. Post-contrast features range from thin peripheral and septal enhancement to focal areas of central enhancement. Pressure erosions, when present, are not accompanied by marrow invasion.
Differential Diagnosis
- Epidermal inclusion cyst: Typically preceded by trauma. Suggestion of debris on imaging.
- Ganglion: Usually asymptomatic. Near joint or tendon sheath.
- Glomus tumor: Often very painful.
- Soft-tissue chondroma: Often mobile. Calcifications typical.
- Tenosynovial giant cell tumor, localized type: Areas of low signal related to hemosiderin. Homogeneous enhancement.
- Digital fibrokeratoma
- Squamous cell carcinoma, subungual.
- Melanoma, subungual.