Intratendinous Fibroma of the Superficial Digital Flexor Tendon within the Carpal Sheath of a Horse.

A 20-year-old British Warmblood gelding was presented for a progressively worsening right forelimb lameness which developed following an intense dressage training session. Initial ultrasound examination revealed a triangular, intrathecal, hypoechoic region within the superficial digital flexor tendon (SDFT) in the proximal, palmar carpal region distal to the accessory carpal bone (ACB), extending 7cm distally into the proximal metacarpal region. No significant improvement in clinical presentation was observed following an eight-week rehabilitation programme. Repeat ultrasound examination revealed an enlarged cross-sectional area of affected tendon. Due to a poor clinical response to conservative treatment, combined with increasingly marked severity of the lameness, the horse was humanely euthanised and the affected SDFT was submitted for macroscopic and histopathological examination at the University of Liverpool. This revealed an approximately 70mm-elongated, focally extensive mass located within the SDFT. On cross-section, the mass was poorly delineated, irregularly triangular, focally haemorrhagic, firm, 15 × 12mm wide and eccentrically placed towards the palmar aspect of the tendon. Histopathological examination identified a moderately to highly cellular, infiltrative, poorly demarcated mesenchymal neoplasm comprised of streams of moderately atypical spindloid cells including bizarre mitoses. Intratendinous fibroma is an uncommonly recorded human neoplasm and this case represents the third reported case of this entity in the horse, the first in an adult horse and the first to be identified in the SDFT.

A Case Series of Five Horses with Superficial Digital Flexor Tendon Lesions in the Carpal Canal.

This case series discusses the clinical presentation, ultrasonographic findings, treatment, and outcome of 5 horses with superficial digital flexor tendon (SDFT) lesions within the carpal canal. The horses' ages ranged from 11-28 years, and presented with an acute, unilateral forelimb lameness which worsened following proximal limb flexion. The presence of a lesion within the SDFT of the carpal canal was accompanied by a mild swelling of the palmar carpal region in most cases. Diagnostic anesthesia of the ulnar nerve, when performed, abolished the lameness. Ultrasound evaluation revealed an increased cross-sectional area (CSA) of the superficial digital flexor tendon compared to the contralateral, sound limb and a loss of tendon fiber architecture within the palmar aspect of the affected tendon, most readily identifiable upon longitudinal ultrasound images. Three out of the five horses returned to their previous level of performance, and two were euthanized. A back at the knee carpal region conformation was associated with a poorer prognosis in these cases. An intratendinous fibroma was identified on histopathological analysis of one-horse following euthanazia, which has been recorded in a complementary short communication.