Canine lobular orbital adenoma: a report of 15 cases with distinctive features

To describe a unique orbital neoplasm in dogs, of lacrimal or salivary gland origin.

Fifteen dogs with lesions consistent with a diagnosis of lobular adenomas involving the orbit were identified from the Comparative Ophthalmic Pathology Laboratory of Wisconsin from 1994 to 2001.

The neoplasm occurred in nine females and six males. Affected dogs ranged in age from 7 to 17 years (mean = 9.7 years). Follow-up information was available for 13 of the 15 cases. The clinical presentation included swollen/hyperemic eyelids (4/15), third eyelid protrusion (3/15), conjunctival mass (6/15), exophthalmos (4/15), resistance to retropulsion (2/15), or strabismus (1/15). In 13 cases the masses were composed of nodular, friable tissue and they were solid in two cases. Histologically, the tissue was found in encapsulated lobules resembling well differentiated lacrimal or salivary glands but completely lacking ducts. Granular PAS-positive material was found within the cytoplasm. There was recurrence in 10 of the 13 cases available for follow-up. Of those cases in which enucleation or exenteration was performed (3/15), there was recurrence of disease in one case. In three cases the dogs were euthanized before recurrence at 3 months, 5 months and 3 years post surgery. None of the deaths was related to the tumor.

In the 15 cases reviewed, lobular adenomas of the orbit presented clinically and histologically as a benign neoplasm of lacrimal or salivary gland origin. Recurrence was likely unless the mass was completely excised, at times requiring orbital exenteration.