Use of computed tomography angiography for the evaluation of a cutaneous haemangioma in a Standardbred horse

Abstract

Cutaneous haeangiomas are benign vascular neoplasms that arise from endothelial cells of blood vessels. Haemangiomas account for 0.6%-4% of all equine cutaneous neoplasms and the fetlock is the most commonly affected site. We describe the use of computed tomography angiography (CTA) for the evaluation of a cutaneous haemangioma located on the plantarolateral aspect of the left hindlimb fetlock of a 9month-old Standardbred colt. Computed tomography angiography of the affected fetlock was performed under general anaesthesia. The medial plantar artery was catheterised and a total volume of 50 ml of iodinated nonionic contrast medium (Iopamidol, 300 mg I/ml, Bracco Imaging Canada) was injected at a rate of 2 ml/s. Following contrast medium administration, the dorsal metatarsal artery and branches including the lateral and medial digital arteries were well demarcated. Two smaller lateral and medial arteries were also identified, forming the vascular network of the metatarsophalangeal joint. At the level of the haemangioma, two tortuous arteries arising from the lateral digital artery were identified, in addition to multiple small branches from nearby cutaneous arteries. These vessels supplied the homogeneously strongly contrast-enhancing cutaneous mass. The initial goal of the CTA study was to map the vascular anatomy for arterial embolisation in conjunction with pharmacological therapy. Considering the involvement of multiple small arterial branches, complete surgical excision along with ligation of the two main supplying arteries was alternatively elected, resulting in a successful long-term outcome. Clinical findingsAt the time of second referral to the Ontario Veterinary College at 9 months of age, no abnormalities were observed on physical examination other than recurrence of the proliferative tissues on the plantarolateral aspect of the left metatarsophalangeal joint. The mass was 5.7 cm dorsoplantar 9 3.4 cm proximodistal 9 1.1 cm lateromedial and characterised by a dark purple colour, welldemarcated margins and a combination of verrucous and smooth surfaces (Fig 2). It was easily movable and appeared attached only to the cutaneous and subcutaneous tissues. Pain was not elicited on palpation and no lameness was noted when the colt was evaluated at the trot.

Perivascular wall tumour presenting as pastern mass in a Standardbred gelding

“…To provide therapeutic options and prognosis for a case where a mass is present, it is essential that the nature of the mass is accurately diagnosed. Vascular neoplasms are rare in the horse and the literature regarding classification of equine vascular neoplasms lacks clarity 3,6–12 . Biopsy is the minimum standard for investigation of a vascular mass, as fine needle aspiration almost always results in nondiagnostic cytology due to poor exfoliation of mesenchymal cells and blood contamination 17 …”

“…Vascular neoplasms are rare in the horse and the literature regarding classification of equine vascular neoplasms lacks clarity. 3,[6][7][8][9][10][11][12] Biopsy is the minimum standard for investigation of a vascular mass, as fine needle aspiration almost always results in nondiagnostic cytology due to poor exfoliation of mesenchymal cells and blood contamination. 17 Whilst many tumour types can be differentiated with standard histology, those that are poorly differentiated or closely resemble others histologically require IHC for accurate diagnosis.…”

“…T here are limited reports of disordered growth of vascular origin in horses and accurate classification has been hindered by inconsistencies in the nomenclature. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Diagnoses of hamartoma, hemangioma, haemangioma, haemangiosarcoma, vascular naevus, lymphangioma, glomus tumour and proliferative angioma exist, but no case of perivascular wall tumour (PWT) has been described in the horse. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] PWT arise from the cellular components of the vascular wall; including pericytes present in the capillary subendothelial lining and vascular smooth muscle cells but excluding the endothelial lining.…”

“…There are limited reports of disordered growth of vascular origin in horses and accurate classification has been hindered by inconsistencies in the nomenclature 1–15 . Diagnoses of hamartoma, hemangioma, haemangioma, haemangiosarcoma, vascular naevus, lymphangioma, glomus tumour and proliferative angioma exist, but no case of perivascular wall tumour (PWT) has been described in the horse 1–15 …”

“…Pericytes are particularly concentrated in the distal limbs, representing a potential contributing factor to the development of a PWT in the pastern region of this horse. Furthermore, increased blood pressure in the equine distal limb is speculated to influence the predilection of equine vascular malformations and neoplasms to the limb 1,3,5,6,8–15 . Other locations are less commonly described 2,6,14 …”