Clinicopathologic Features, Surgical Treatment, and Pathological Characterization of Canine Dacryops with Different Localization.

Lacrimal cysts (dacryops), which involve lacrimal tissue, are uncommon in dogs with an obscure/unclear pathogenesis. Compared to the current available literature, this report describes the clinicopathologic and immunohistochemical features of two cases of unusual dacryops in brachycephalic dogs. A three-year-old male Cane Corso was referred with a 1-month history of swelling ventromedial to the left eye associated with blepharospasm and epiphora. Furthermore, a severe lower and upper eyelid entropion and a deep corneal ulcer were present. B-mode ultrasonography and a CT scan revealed a subcutaneous cyst, closely adherent to the maxillary bone. Surgical removal and the correction of entropion were performed. No recurrence and/or complication was detected by seven-year follow-up. Histopathology revealed a cystic structure with single- to double-cell-layered, nonciliated, cuboidal epithelia. Alcian blue stain revealed rare, disseminated goblet cells admixed with epithelial cells. The epithelium was strongly Cytokeratin-positive by immunohistochemistry and appeared lined by several layers of smooth muscle actin (SMA)-positive myoepithelial cells. A 1-year-old male French Bulldog with a 3-month lesion of the third eyelid of the right eye. The lesion (15 mm × 7 mm) beneath the conjunctiva appeared pale-pink, smooth, and multilobulated. Excision was performed by blunt dissection through the conjunctiva on the palpebral surface of the third eyelid. Recovery was uncomplicated, and no recurrence has been noted at three-year follow-up. Cytology of the cystic fluid and histopathology and immunohistochemistry of the cyst wall revealed findings for case 1. To further characterize the SMA-positive spindle cells located directly beneath the cyst-lining epithelium, double-color immunofluorescence for SMA and p63 (a myoepithelial cell marker) was performed on the sample from case 2. The analysis revealed that the SMA-positive cells lacked p63 expression, indicating a non-myoepithelial phenotype. The histological findings in our cases are consistent with previous reports of canine dacryops. The positivity of immunohistochemical staining for SMA in cells directly beneath the epithelium of dacryops in the cases here described in two brachycephalic dogs is consistent with previous reports in dogs and horses but in contrast with a retrospective study about a human dacryops. These results support the conclusion that the pathogenesis of dacryops in dogs should exclude failure of ductular "neuromuscular" contractility.