title: COMPUTED TOMOGRAPHIC APPEARANCE OF MELANOMAS IN THE EQUINE HEAD: 13 CASES.
abstract: Melanomas are one of the most common neoplasms in the horse and are frequently found in the head region. There is a genetic predisposition in horses with a gray hair coat. Computed tomography (CT) is frequently used in referral practice to evaluate the equine head but there are few reports describing the CT appearance of melanomas in this location. The aim of this retrospective, case series study was to describe characteristics in a group of horses with confirmed disease. Case records from two referral hospitals were reviewed, and 13 horses were identified that had undergone CT of the head, with a diagnosis of melanoma based on cytology, histopathology, or visual assessment of black (melanotic) tissue. A median of 11 melanomas was identified per horse (range 3-60), with a total of 216 masses. Melanomas were found most frequently in the parotid salivary gland, guttural pouches, surrounding the larynx and pharynx and adjacent to the hyoid apparatus. In noncontrast CT images, all melanomas were hyperattenuating (median; 113.5 Hounsfield units (HU), IQR; 26 HU) compared to masseter musculature (median; 69 HU, IQR; 5.5 HU). Fifty-six (25.9%) masses were partially mineralized and 41 (19.4%) included hypoattenuating areas. Histopathological assessment of these melanomas suggested that the hyperattenuation identified was most likely a result of abundant intracytoplasmic melanin pigment. Melanomas of the equine head appeared to have consistent CT features that aided detection of mass lesions and their distribution, although histopathological analysis or visual confirmation should still be obtained for definitive diagnosis.
authors.affiliation: Department of Clinical Sciences and Services, The Royal Veterinary College, Hawkshead Lane, Hatfield, AL9 7TA, UK.
authors.forename: Jonathon
authors.initials: J
authors.lastname: Dixon
authors.affiliation: Department of Clinical Sciences and Services, The Royal Veterinary College, Hawkshead Lane, Hatfield, AL9 7TA, UK.
authors.forename: Ken
authors.initials: K
authors.lastname: Smith
authors.affiliation: Department of Clinical Sciences and Services, The Royal Veterinary College, Hawkshead Lane, Hatfield, AL9 7TA, UK.
authors.forename: Justin
authors.initials: J
authors.lastname: Perkins
authors.affiliation: Bell Equine Veterinary Clinic, Butchers Lane, Mereworth, Kent, ME18 5GS, UK.
authors.forename: Ceri
authors.initials: C
authors.lastname: Sherlock
authors.affiliation: Bell Equine Veterinary Clinic, Butchers Lane, Mereworth, Kent, ME18 5GS, UK.
authors.forename: Tim
authors.initials: T
authors.lastname: Mair
authors.affiliation: Department of Clinical Sciences and Services, The Royal Veterinary College, Hawkshead Lane, Hatfield, AL9 7TA, UK.
authors.forename: Renate
authors.initials: R
authors.lastname: Weller
mesh_terms: D000818:Animals; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000662:veterinary*; D006734:Horse Diseases / Q000000981:diagnostic imaging*; D006736:Horses; D008297:Male; D008545:Melanoma / Q000000981:diagnostic imaging / Q000662:veterinary*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000662:veterinary*
keywords: computed tomography; equine; melanoma; neoplasia