Imaging Diagnosis—equine Mast Cell Tumor

Abstract

Equine mast cell tumors are typically benign solitary growths of the head, neck, trunk, or limbs. When involving the limbs, these masses tend to be adjacent to joints without involving them. In radiographs there is often a well-circumscribed soft tissue mass with granular mineralization. The Arabian breed appears to be over represented. Surgical removal is usually curative. In this report, we describe the diagnosis, clinical features, and management of mast cell tumors in the rear limb of a horse.

Unilateral testicular mastocytoma in a Peruvian Paso stallion

“…The observation of numerous eosinophils dispersed within the sheets of neoplastic mast cells in this case was not described in the single previous report of testicular mastocytoma. The presence of eosinophils dispersed amongst sheets of mast cells is similar to the descriptions of cutaneous mast cell neoplasms of horses (Malikides et al 1996;Cole et al 2007). Marked peripheral blood eosinophilia has also been observed in some cases of cutaneous mast cell neoplasia; a similar finding was not made in this case of testicular mastocytoma as a complete blood count was not performed (Reppas and Canfield 1996).…”

“…A congenital multifocal cutaneous form has been reported in foals at or shortly after birth, which is characterised by spontaneous regression (Prasse et al 1975). The second more common form is typically associated with the production of benign, solitary nodules of the head, neck, trunk or limbs of mature horses of all ages (Whitler et al 1994;Malikides et al 1996;Reppas and Canfield 1996;Johnson 1998;Taylor et al 2005;Cole et al 2007). The cutaneous form has been most commonly reported in male Arabian horses where most affected horses had favourable outcomes following complete surgical excision, although metastases to local lymph nodes has been reported in isolated cases (Reppas and Canfield 1996;Carr 2006;Cole et al 2007).…”

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

“…; Cole et al . ). Unlike in other species, there is no grading scale for equine MCT and they are rarely malignant (Clarke et al .…”

Tracheal obstructive mastocytoma in a pony

“…Mast cell tumours (also called mastocytosis or mastocytoma) are uncommon in horses. 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).…”