Conjunctival myxoma in a dog: clinical and histopathological features

A 9-year-old male Bull Terrier was presented for a 3-month history of a progressive, non-painful conjunctival mass of the right eye. The mass was exophytic and located in the temporal bulbar conjunctiva. No adhesion to the sclera was detected. A presumptive clinical diagnosis of a conjunctival neoplasia was made. Complete physical and ophthalmological examinations of the dog, as well as complete blood count, serum biochemical analysis, urinalysis, thoracic radiography, echocardiography and abdominal ultrasonography, were performed. The mass was surgically removed and a double freeze-thaw cycle of cryotherapy was performed locally. Histological examination of the removed tissue showed a well-delineated, non-encapsulated mass composed of spindle cells in loose myxomatous stroma. No nuclear atypia was observed in the tumour cells. A positive Alcian blue stain confirmed the mucin origin of the stroma. Tumour cells stained positive on immunohistochemistry for vimentin and negative for cytokeratins. A diagnosis was made of conjunctival myxoma. No evidence of local recurrence or distant metastases was identified during the 24-month follow-up period.

To the best of the authors' knowledge, this is the first report on a conjunctival myxoma in dogs.