CT IMAGING HELPS FIND MELANOMA TUMORS

A recent study from England has shown that computed tomographic (CT) imaging can detect melanoma tumors “hidden” in a horse’s head.

Tumors of the skin more common in gray horses, equine melanomas are most frequently found underneath and at the base of the tail and around the genital region. The rounded and dark tumors often bulge, giving the skin a “cluster of grapes” appearance that is easy to spot. In contrast, internal melanoma tumors can be difficult to detect.

“Unfortunately, melanomas can appear absolutely anywhere in the body including in the thoracic and abdominal cavities,” says Jonathon Dixon, BVetMed, MRCVS, of the Royal Veterinary College.

To investigate the occurrence of melanomas within the head, Dixon and his fellow researchers reviewed the records of 13 horses with confirmed melanoma who had CT scans taken as part of the diagnostic process. CT scans use an x-ray beam to image “slices” of a structure and can often pinpoint lesions that go undetected by conventional radiographs.

The researchers identified a total of 216 melanomas affecting the head, finding from three to 60 growths per horse, with a median of 11. The tumors were most frequently located in the salivary glands, guttural pouches, around the larynx and pharynx , and near the hyoid apparatus, the bone structure that holds the tongue in place. Although not common, says Dixon, “an additional interesting finding was the presence of some masses within the tongue itself.”

Dixon says that in many of the study cases, more melanomas were identified using CT than had been identified in the initial clinical exam, suggesting that “CT may reveal more information regarding the lesion extent than any other currently used technique.”

The ultimate effect of melanomas within a horse’s head varies, says Dixon. “Masses in the head can cause a variety of problems depending on the specific location. For example, a lesion around the tongue or hyoid apparatus may cause difficulty in eating or swallowing food,

CT scans use an x-ray beam to image “slices” of a structure and can often pinpoint lesions that go undetected by conventional radiographs.