Rapidly growing primary malignant teratoid medulloepithelioma of the ciliary body in a gelding

Abstract

Intraocular medulloepithelioma is a relatively rare tumour in horses which is difficult to differentiate from retinoblastoma. The rate of growth of this tumour has not been investigated so far. We present a case of a primary intraocular teratoid malignant medulloepithelioma in a four-year-old gelding that was unilaterally blind at presentation. Repeated examination revealed rapid growth of the tumour. After enucleation of the affected eye, the horse returned to its former level of performance without recurrence for 12 months postoperatively. The histological and immunohistochemical examination of the mass clearly confirmed the malignancy of the tumour. Clinicians should be aware of the potential malignant behaviour of intraocular neoplasias. Immunohisto chemistry plays an important role in the final diagnosis

Clinical behavior of intraocular teratoid medulloepithelioma in two‐related Quarter Horses

“…GFAP is an intermediate filament present in neural cells such as astrocytes and ependymal cells. Interestingly, two previous equine case reports performing IHC on medulloepitheliomas were negative for GFAP . This may represent a variability in stages of differentiation in the tumor cells.…”

“…A 5‐year‐old Standardbred mare's neoplasia was described as malignant due to its histologic characteristics . In the second case, the rapid expansion and histologic features of the tumor in a 4‐year‐old warmblood gelding prompted the diagnosis of malignancy; however, there was not extension beyond the confines of the globe . Follow‐up was available through 12 months and did not reveal any recurrence.…”

“…However, the occurrence of systemic metastasis was 8% of cases, each of whom had extrascleral extension of the tumor due to a delay in diagnosis. Three previous reports in horses describe malignant lesions . A 5‐year‐old Standardbred mare's neoplasia was described as malignant due to its histologic characteristics .…”

“…Primary intraocular neoplasms in the equine have been reported but are uncommon . Intraocular medulloepithelioma is a rare neoplasm that forms from the primitive medullary epithelium, a derivative of the inner layer of the embryologic optic cup .…”

“…Medulloepitheliomas are designated teratoid if they show heterotopic elements of hyaline cartilage, rhabdomyoblasts, undifferentiated mesenchymal cells, or neuroglial cells in addition to proliferation of the medullary epithelium . Teratoid medulloepitheliomas have been previously reported in horses as well as in humans and a variety of veterinary species . In people, where they are most studied, these tumors are usually diagnosed in children (median age of 5 years).…”