Intratendinous Fibroma of the Superficial Digital Flexor Tendon within the Carpal Sheath of a Horse.
Authors: Rich Andrew Frederick, Ricci Emanuele, Gates Sophie, Hinnigan Guy Joseph, Owen Kathryn Rose
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Intratendinous Fibroma of the Superficial Digital Flexor Tendon A 20-year-old British Warmblood gelding presented with progressive right forelimb lameness following intense dressage training, and ultrasonographic examination revealed a triangular, hypoechoic mass within the superficial digital flexor tendon (SDFT) spanning approximately 7 cm from the proximal carpal region into the proximal metacarpal area. Despite eight weeks of conservative rehabilitation, the horse showed clinical deterioration with enlargement of the affected tendon on repeat ultrasound, ultimately leading to humane euthanasia and post-mortem examination. Histopathological analysis confirmed an intratendinous fibroma—a moderately to highly cellular mesenchymal neoplasm with atypical spindle cells and bizarre mitotic figures, measuring approximately 70 mm in length and positioned eccentrically within the tendon. This represents only the third documented case of intratendinous fibroma in equine literature and notably the first confirmed in an adult horse and within the SDFT specifically, suggesting practitioners should maintain awareness of this rare but significant differential diagnosis when encountering tendinous masses unresponsive to standard rehabilitative protocols. The poor prognosis associated with this neoplasm's infiltrative nature and lack of response to conservative management warrants early consideration of advanced imaging and diagnostic sampling when clinical signs progress despite appropriate initial treatment.
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Practical Takeaways
- •Intratendinous fibromas should be considered in the differential diagnosis of progressive forelimb lameness that fails to respond to conservative treatment, particularly when ultrasound shows an enlarging hypoechoic lesion within the SDFT
- •Serial ultrasound imaging is valuable for monitoring lesion progression and identifying lack of response to rehabilitation, which may indicate need for alternative management decisions
- •Poor prognosis cases with progressive necrosis/enlargement despite treatment warrant early consideration of euthanasia to prevent further compromise and suffering
Key Findings
- •Third reported case of intratendinous fibroma in horses and first documented in an adult horse within the SDFT
- •Lesion presented as a 70mm elongated, poorly demarcated mass within the SDFT in the proximal carpal region, measuring 15×12mm on cross-section
- •Progressive worsening of lameness occurred despite 8-week conservative rehabilitation, with repeat ultrasound showing enlargement of affected tendon cross-sectional area
- •Histopathology confirmed a moderately to highly cellular, infiltrative mesenchymal neoplasm with atypical spindloid cells and bizarre mitoses