Treatment of an invasive equine mast cell tumour in the extensor carpi radialis by extensive tenomyectomy and local corticosteroid injections

Abstract

Summary Equine mast cell tumours (MCT) have been reported to occur in the skin, respiratory tract, oral cavity, synovial structures and eye. These tumours are typically locally invasive and nonaggressive. In this case, a MCT was located in the extensor carpi radialis (ECR) and was highly infiltrative. Excision of the ECR and local corticosteroid injection was curative and resulted in a good functional outcome. A 12‐year‐old Thoroughbred gelding presented for lameness, swelling and pruritus associated with the right antebrachium. Sonographic changes were suggestive of severe tenosynovitis and purulent material in the ECR. Surgical exploration revealed maceration at the ECR musculotendinous junction. The extensor sheath contained a large quantity of caseous material and serosanguinous fluid. The ECR tendon and 75% of the muscle was excised. Cytology and histopathology were consistent with a MCT that infiltrated the surgical margins. Post‐operatively the horse was treated with multiple local corticosteroid injections along the incision. Right forelimb movement was initially limited, however, there was steady improvement over 3 months with increasing exercise. At 18 months post‐operatively, no lameness was detectable in the walk, trot or canter and no recurrence of MCT was apparent. The horse appeared to compensate for loss of the ECR by using the biceps during the swing phase. Partial excision and local corticosteroid treatment can be curative for cases of invasive MCT. Extensive excision of the ECR is a viable treatment option for neoplasia or other conditions affecting the ECR in the horse.

Pathology of equine extensor tendons: Can they function without them?

“…Functional loss of an extensor tendon may occur due to laceration, rupture or surgical resection due to chronic inflammation and infection of the tendon and its surrounding synovial sheath. Removal of tumour tissue, as in the case report by Johnston and Zedler () from this issue, is a unique indication for extensor tendon resection. One previous report describes surgical removal of a lipoma that had formed around the common and long digital extensor tendons and involved the dorsal aspect of the common digital extensor tendon sheath; the tendon was preserved with this procedure, and only the mass itself and the proximal aspect of the involved tendon sheath were removed (Hammer et al .…”

Equine non‐septic tenosynovitis: A systematic literature review of site‐specific pathological lesions, outcomes and surgical complications

“…From 1969 to 2021, a total of 85 studies describing non-septic tenosynovitis in the horse were included (Table S1). [1][2][3][4][5][6][8][9][10][11][12][15][16][17][18]21,23,24,26,27,[29][30][31]33,36, Of these studies, 80/85 (94%) papers limited the scope of the manuscript to a single tendon sheath [1][2][3][4][5][6][8][9][10][11][15][16][17][18]21,23,24,26,27,[29][30][31]33,36,[77][78]…”

“…The frequency of pathological findings and specific tendon sheath affected varies with breed and discipline; however, non-septic tenosynovitis is more commonly reported in adult horses with an expectation of athleticism. 3,4 Intrathecal pathological lesions reported in non-septic tenosynovitis can generally be classified as: intrathecal tendon tears [3][4][5] ; intrathecal desmitis 6 ; proliferative synovitis of unknown cause 7 : neoplasia [8][9][10][11] ; or idiopathic tenosynovitis. 12 Intrathecal tendon tears also include the manica flexoria, a reflection of the superficial digital flexor tendon which is histologically indistinguishable at its attachment site to the superficial digital flexor tendon.…”

Tracheal obstructive mastocytoma in a pony

“…Most occur subcutaneously, involved the dermis, and were commonly seen on the head, neck (Brown et al, 2007), trunk and extremities (Cole et al, 2007; Lykkjen et al, 2006; McEntee, 1991; Samii et al, 1997). Many other localisations were also described: scleral (Ward et al, 1993), corneal (Halse et al, 2014), palpebral (Shnaiderman‐Torban et al, 2017), nasal, pharyngeal (Richardson et al, 1994), laryngeal (Mair & Krudewig, 2008), tracheal (Wenger & Caron, 1988), testicular (Brown et al, 2008), intraosseous (Ritmeester et al, 1997), intra‐articular (Taylor et al, 2005), intra‐thecal (Johnston & Zedler, 2018; Leadbeater et al, 2010, Uehlinger et al, 2010, Zetterström et al, 2017) and a multicentric form (Millward et al, 2010; Tan et al, 2007). Most mast cell tumours are benign but require treatment for cosmetic reasons or because of undesirable local effects (Mair & Krudewig, 2008).…”