Orbital multilobular tumour of bone in a dog

A multilobular tumour of bone with left orbital involvement was diagnosed at post mortem examination in an eight-year-old German shepherd cross dog. The tumour resulted in progressive exophthalmos with lateral deviation of the left eye. Radiographs revealed that the mass was mineralised and originated from the left frontal bone with invasion of the left frontal sinus and destruction of the cribriform plate. This is the third reported case of this type of tumour involving the orbit of the dog and thus multilobular tumour of bone should be considered as a differentia] diagnosis of exophthalmos.