Complex maxillary malformation with orbital zygomatic mucocele in a puppy: a case report

Purpose: To describe a zygomatic gland mucocele and concomitant maxillary malforma- tion in a dog. A 7-month-old, male, mixed breed dog had a recent-onset of unilateral exoph- thalmos with third eyelid protrusion and a gradually enlarged swelling in the right temporal region. Methods: Physical and ophthalmic examinations, imaging, surgery and histology of the lesion were performed. Results: A compressing, painful right retrobulbar mass was clinically suspected and confirmed by ultrasound. Computed tomography revealed a large multiloculated cystic-like lesion of the right zygomatic gland projecting into the orbital space, displacing the eyeball. The ipsilateral molar part of the maxillary bone were underde- veloped with multiple abnormal unerupted mandibular crowded molar teeth in the premolar region. Modified lateral orbitotomy and selective caudal maxillary bone access were per- formed to provide ventral exposure of the orbit and dental extraction, while minimizing trauma to the globe and supporting structures. The pseudocyst was removed and the wall sampled for histology. Sections were characterized by acini of zygomatic gland embedded in a thick granulation tissue delineated in a border by abundant fibrin and amorphous hyaline homogeneous material (salivary secretion), partially infiltrated by macrophages consistent with sialocele. Clinical and imaging examinations six months after surgery showed no recur- rence of the mucocele or ocular implications. Conclusions: We described a complex case of exophthalmos due to zygomatic mucocele in a puppy with ipsilateral maxillary hypoplasia. A possible relationship between these two conditions could be hypothesized on the basis of advanced imaging features. Early diagnosis and management prevented later ocular complications.