EQUUS - - EQ Medical Front -

nic­ti­tat­ing mem­brane

Although sur­gi­cal re­moval is one of the most ef­fec­tive means of treat­ing squa­mous cell car­ci­noma (SCC) tu­mors of the nic­ti­tat­ing mem­brane, a new study un­der­scores the need for care­ful mon­i­tor­ing there­after.

Re­searchers at the Univer­sity of Penn­syl­va­nia’s New Bolton Cen­ter ex­am­ined the records of 50 horses treated at the univer­sity’s vet­eri­nary hos­pi­tal for a mass of the nic­ti­tat­ing mem­brane---the thin tis­sue also known as the “third eye­lid” that sweeps over the globe from the cor­ner of the eye.

Forty-five of the masses were neo­plas­tic0 and 37 masses were con­firmed as squa­mous cell car­ci­noma. In 19 of the study horses, surgery alone---ei­ther par­tial or com­plete re­moval of the nic­ti­tat­ing mem­brane---was used to treat the mass. Another 31 horses had surgery fol­lowed by some form of top­i­cal chemo­ther­apy. “Chemo­ther­apy is pre­scribed in some cases due to the sever­ity of the le­sion or de­pend­ing on the clin­i­cian per­form­ing the pro­ce­dure,” ex­plains Ni­cole Scher­rer, DVM.

Follow-up re­ports from at least one Ref­er­ence: “Char­ac­ter­i­za­tion and out­come fol­low­ing ex­ci­sion of masses in the nic­ti­tat­ing mem­branes of horses: 50 cases (1998-2012),” Jour­nal of the Amer­i­can Vet­eri­nary Med­i­cal As­so­ci­a­tion, Oc­to­ber 2014 year after surgery showed that there was a re­cur­rence of neo­pla­sia in 20 per­cent of the study horses, with an av­er­age time to re­cur­rence be­ing two years and three months. Over­all, use of chemo­ther­apy did not have a sig­nif­i­cant ef­fect on the rate of re­cur­rence, although the five study horses who re­ceived a spe­cific type of chemo­ther­apy ---top­i­cal 0.4 per­cent mit­o­mycin C---had no re­cur­rence.

Neo­pla­sia re­cur­rence led to eu­thana­sia in six of the horses. “SCC does not typ­i­cally in­vade vi­tal or­gans such as the lungs,” says Scher­rer. “How­ever, it does in­vade the si­nus, soft tis­sues of the head and even the brain in se­vere cases. Most cases of eu­thana­sia are due to poor qual­ity of life due to de­for­ma­tion of bone, ob­struc­tion of air­flow or per­sis­tent dis­charge.”

When a por­tion of a horse’s third eye­lid was re­moved prior to re­fer­ral to New Bolton Cen­ter, the risk of mor­tal­ity was sig­nif­i­cantly higher, com­pared to horses who did not un­dergo re­sec­tion prior to re­fer­ral. “The third eye­lid is easy to re­move in the horse, and our re­sults sug­gest that in­stead of biopsy the struc­ture should be re­moved in its en­tirety,” says Scher­rer. “Un­for­tu­nately, third eye­lid masses can be quite dev­as­tat­ing. I would sug­gest sur­gi­cal re­moval as soon as pos­si­ble with top­i­cal chemo follow-up if the mass is di­ag­nosed as neo­plas­tic or pre­neo­plas­tic.”

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