Dacryops (Lacrimal Cyst) in Three Young Labrador Retrievers
This case series constitutes a report of dacryops in multiple Labrador retrievers and the use of smooth-muscle actin immunostaining to confirm the lacrimal duct origins of the cyst wall. Three Labrador retrievers were presented with a history of a slowly enlarging mass adjacent to the left medial canthus. Ultrasonography of the masses revealed they were each spherical, thin-walled cystic structures. Aspiration cytology was performed in two cases revealing mixed inflammation and absence of detectable microorganisms. Dacryocystorhinography of the left nasolacrimal system performed in two cases revealed a normal nasolacrimal system that was closely associated, but not communicating with, the cystic mass in both cases. Surgical excision of all cysts was curative. Histopathology and positive immunohistochemical staining for smooth-muscle actin confirmed a diagnosis of dacryops in all cases.
Introduction
Dacryops is a cyst or ectasia originating from lacrimal glandular ductal tissue (both intraglandular and extraglandular). Dacryops are rare in domestic animals and are infrequently reported in the veterinary literature.1–6 The exact pathogenesis for the development of dacryops is uncertain, and no specific etiology has been elucidated in reported canine cases.1,2,5,6 In the dog, the main lacrimal gland lies under the periorbita in the dorsolateral aspect of the orbit, and the accessory lacrimal gland is located in the third eyelid. Ectopic or choristomatous lacrimal gland tissue has been reported in dogs.6 Cyst formation may occur in any location where lacrimal gland tissue is present.1,3,4,6 Management of dacryops is primarily surgical, with complete excision being curative.7–9 This case series outlines three cases of dacryops in young Labrador retrievers; the dacryops originated from ectopic periocular lacrimal gland ductal tissue, and cases were treated successfully by surgical excision. The young age of the dogs, cyst location, and lack of historical trauma suggest a congenital etiology.
Case Reports
Case No. 1
A 1-year-old, castrated male Labrador retriever was referred for evaluation of chronic swelling adjacent to the medial canthus of the left eye (OS) and epiphora OS. The swelling had been enlarging slowly for 6 months prior to presentation. Surgical excision of the mass was attempted by the referring veterinarian 5 days prior to referral, but it was aborted due to the close proximity of the mass to the nasolacrimal apparatus. The dog was not receiving any medications at the time of referral.
Initial ophthalmic examination revealed a well-demarcated, ovoid, raised, turgid, nonulcerated, subcutaneous mass measuring 15 × 10 mm adjacent to the medial canthus and medial inferior eyelid margin OS [Figure 1A]. Neuroophthalmic examination including menace response, direct and consensual papillary light response, palpebral reflex, and vestibular ocular reflex was normal in both eyes (OU). Applanation tonometrya revealed normal intraocular pressures of 16 and 15 mm Hg in the right eye (OD) and OS, respectively. Values of the Schirmer I tear testb were 25 and 23 mm per minute OD and OS, respectively. Slit-lamp biomicroscopy and indirect ophthalmoscopy revealed no anterior or posterior segment abnormalities. Jones I test (i.e., fluorescent dye passage) performed by application of fluorescein dyec topically to each eye was positive OD and negative OS. Jones II test was performed OS with 5 mL of sterile eye-irrigating solution,d and a 24-gauge intravenous (IV) catheter sheathe was inserted into the superior canaliculus, revealing positive fluid and fluorescein stain passage through the corresponding ventral punctum and nare. The size of the mass remained unchanged after nasolacrimal flush. No other abnormalities were detected on physical examination.
Results of a complete blood count, serum biochemical analysis, and urinalysis were within reference ranges. Ultrasonography of the medial canthal mass using a 10- MHz probe revealed a spherical, thin-walled cystic structure. A transcutaneous, fine-needle aspirate of the mass was obtained, yielding 0.5 mL of turbid brown fluid. Cytological examination of the aspirate revealed mixed inflammation (primarily nondegenerate neutrophils) with no organisms. Positive contrast dacryocystorhinography of the left nasolacrimal system delineated normal nasolacrimal canaliculus, sac, and duct; no communication with the cystic mass was detected. Contrast media,f injected via a 25-gauge needle into the mass, outlined a solitary cystic structure with no communication to adjacent tissues or evidence of foreign body. The cyst was superimposed over the nasolacrimal system on all radiographic views. Further evaluation with computed tomography (CT) scan confirmed a normal nasolacrimal system and an independent, but closely juxtaposed, cystic mass at the medial canthus OS. No bony invasion was apparent [Figure 2].
Surgical removal of the mass was recommended as the most likely means of effecting a cure, to prevent further occlusion of the left nasolacrimal duct, and to provide a histopathological diagnosis. The inferior canaliculus was cannulated with a 3.5 French red-rubber catheterg to demarcate proximal nasolacrimal structures during dissection of the cyst. A 1.5-cm curvilinear incision was made parallel to the eyelid margin through the skin, orbicularis oculi, and levator nasolabialis muscles overlying the blue-colored cystic mass. The cyst was carefully dissected free of its soft-tissue attachments using a combination of sharp and blunt dissection, and it was removed in its entirety [Figure 3].
A 1-mm rent in the canaliculus occurred during surgical excision because of the intimate association between the inferior canaliculus and cyst wall. Meticulous apposition of the tissue around the canalicular incision was completed with a simple interrupted suture of 7-0 polygalactin.h The subcutaneous tissues were closed in two layers using 4-0 polygalactin in a simple continuous pattern, and the skin was closed with 4-0 braided nyloni in a Ford interlocking pattern. The indwelling nasolacrimal catheter was left in situ postoperatively to promote mucosal epithelialization of the incised inferior canaliculus and to prevent stricture by granulation tissue. The catheter was sutured to the periocular skin and adjacent to the left nare using 4-0 braided nylon in a simple interrupted pattern. The dog was discharged the following day, and the owner was instructed to administer meloxicamj for 5 days and triple antibiotic ophthalmic solutionk for 3 weeks. The owner was recommended to have the dog wear an Elizabethan collar at all times until recheck examination.
Recheck examination 2 weeks postoperatively revealed adequate healing of the periocular surgical site, and skin sutures were removed. At recheck examination 3 weeks following surgery, the catheter was removed and the patency of the nasolacrimal system was confirmed by Jones I test. Topical use of triple antibiotic ophthalmic solution was discontinued 5 days after catheter removal. Ophthalmic examination 4 months following surgery was normal, with complete resolution of the mass and epiphora. Follow-up information obtained from the owner 1 year after surgery indicated the mass and epiphora had not recurred.
Case No. 2
A 10-month-old, spayed female Labrador retriever was referred for evaluation of a slowly enlarging swelling of 5 months’ duration, located at the left medial canthus and epiphora OS. Treatment by the referring veterinarian with oral antibiotics and corticosteroids had not been effective. Ophthalmic examination abnormalities were limited to a turgid, round, 15 × 20-mm, subcutaneous mass adjacent to the medial canthus and medial inferior eyelid margin OS [Figure 1B]. Intraocular pressure measurements were 16 and 15 mm Hg OD and OS, respectively. Schirmer I tear test values were within normal reference ranges (18.89±2.62 mm per minute),10 and no fluorescein stain uptake was detected in either eye. Jones I test was positive OD and negative OS. Jones II test OS revealed positive fluid and fluorescein stain passage through the corresponding ventral punctum and nare, and the size of the mass remained unchanged after nasolacrimal flush.
Ultrasonography of the mass revealed a spherical, thin-walled cystic structure. Cytological examination of the aspirated cyst fluid revealed mild suppurative to mixed inflammation with no microorganisms detected. Bacteria were not isolated from the aspirated fluid. Dacryocystorhinography of the left nasolacrimal system delineated normal nasolacrimal structures and demonstrated no communication with the cystic mass, which was located rostral to the canaliculus. A magnetic resonance imaging (MRI) study with existing contrast media still present in the nasolacrimal apparatus was performed with additional injection of contrast into the cystic mass and confirmed isolation of the cyst.
Excision of the mass was performed under general anesthesia, and a 1-mm laceration occurred in the inferior lacrimal canaliculus during mass removal. The laceration was closed, and the indwelling nasolacrimal catheter was left in situ as described for case no. 1. Postoperative care was similar to that described for case no. 1. The nasolacrimal catheter was removed 3 weeks following surgery, and patency of the nasolacrimal system was confirmed by Jones I test. Follow-up information per the owner 1 year after surgery indicated the mass and epiphora had not recurred.
Case No. 3
An 8-month-old, spayed female Labrador retriever was referred for evaluation of a swelling of 6 months’ duration at the left medial canthus. The swelling had been aspirated and drained by the referring veterinarian 1 month prior to presentation, but the mass had refilled completely by the time of examination. Physical examination abnormalities were limited to OS and periocular structures. Applanation tonometry revealed normal intraocular pressures of 16 and 15 mm Hg OD and OS, respectively. Values of the Schirmer I tear test were 22 and 21 mm per minute OD and OS, respectively. A subcutaneous swelling measuring approximately 7 × 7 mm was found at the medial inferior eyelid, and bilateral retinal dysplasia was present. Positive Jones I and II tests were observed OU. Imaging diagnostics and fluid analysis were recommended to further characterize the lesion, but these were declined by the owner due to financial constraint.
Excision of the mass was completed under general anesthesia after cannulating the left nasolacrimal system with a 3.5 French red-rubber catheter. The deepest portion of the cyst was intimately associated with the inferior nasolacrimal canaliculus, which was incised to ensure complete cyst removal. This rent was repaired with two simple interrupted sutures of 8-0 polygalactin. The subcutaneous tissue and skin were closed routinely. The nasolacrimal catheter was left indwelling and sutured to the skin using a finger trap pattern. Postoperative care was similar to that described for case no. 1. The dog recovered uneventfully, and the indwelling catheter was removed 3 weeks following surgery without complication. No evidence of cyst recurrence has been reported within 1 year of follow-up.
Histopathology of the masses from all three dogs revealed cysts with single to double cell-layered, nonciliated, cuboidal epithelial lining with mild submucosal fibrosis and mixed inflammation composed of lymphocytes, plasma cells, and macrophages [Figures 4A–4C]. In some areas, the epithelium was flattened to a squamous type, and this was attributed to pressure atrophy. Immunohistochemical staining for smooth-muscle actin performed in all cases revealed several layers of attenuated slender cells directly beneath the epithelium, positively expressing this antigen. This finding indicates the presence of myoepithelial cells at the cyst lining, consistent with a glandular duct [Figure 5]. Control samples of a normal canaliculus and lacrimal gland with ductal tissue were subjected to immunohistochemical staining for smooth-muscle actin. The lumen of normal canaliculus was lined by stratified squamous epithelium and showed negative immunoreactivity for smooth-muscle actin [Figure 6A]. The normal lacrimal glandular and ductal tissue was strongly positive for smooth-muscle actin [Figure 6B].
The presence of myoepithelial tissue is a normal finding in lacrimal ductal tissue, but the presence of myoepithelial tissue in the canaliculus has never been evaluated in dogs.11 Based on this, positive smooth-muscle actin staining in the three cases presented here supported the diagnosis of dacryops (a cyst of lacrimal glandular ductal tissue). The tissue of origin was most likely ductal tissue of ectopic lacrimal tissue since canine lacrimal tissue does not normally exist in the medial canthus.
Discussion
Cysts of the periorbital region are rare in domestic animals.5 Reported periorbital cysts involving or closely related to the nasolacrimal system include dacryops,2,6,12 cystic dilatation of the canaliculi (canaliculops)13 and the nasolacrimal duct,14,15 periorbital epidermoid cysts,16 maxillary bone epithelial cysts,17 and cysts of the frontal and nasal sinuses.5 In the three Labrador retrievers in this report, the size, anatomical location, and patency of the nasolacrimal system were normal based on positive Jones II tests in all cases and dacryocystorhinography and advanced imaging in two of the cases. No connection between the nasolacrimal system and the cyst was identified in any of the dogs. Histopathology of the cyst was identical to that of normal lacrimal ductal tissue and compatible with previously reported dacryops.6,18 Positive immunohistochemical staining for smooth-muscle actin confirmed the presence of myoepithelial cells under the cyst walls, consistent with glandular ductal origin.19 To the authors’ knowledge, this finding has not been previously evaluated or reported in the literature. In the cases presented here, cystic lacrimal glandular ductal tissues in the periocular tissue were located ectopically (as choristomas), consistent with other accounts of canine dacyrops.1,5
Eight cases of dacryops have been reported in the veterinary literature. Four of the reported canine dacryops cases occurred in young basset hounds, indicating a potential breed predisposition.1,2,4–6 This case series represents the first report of Labrador retrievers with dacryops. A previous report of a maxillary bone epithelial cyst in a Labrador retriever has been published. No familial relationship existed between the three dogs. The unilateral presentation and young age of these dogs were consistent with previous reports of canine dacryops.2,6
In this case series, the left periocular area was affected in all dogs; the significance of this finding is unknown. Potential causes for the cystic lesions include congenital malformations, chronic inflammation, traumatic disruption of glandular or ductular tissue, and neoplastic processes.1,5,12,20 The exact pathogenesis is unclear. Studies in humans suggest that periductal inflammation or trauma stimulates hypersecretion, destroys neuromuscular contractility of the lacrimal gland duct, weakens the duct walls, and finally results in passive ductal dilatation with cyst formation.7 In the dogs reported here, no histological or historical evidence was found that correlated with known inciting causes of dacryops. However, ectopic lacrimal glandular and ductal tissue has only been reported in dogs with dacryops, suggesting that the presence of ectopic lacrimal tissue predisposes the dog to or causes dacryops.1,2 The signalment, clinical appearance, and lack of traumatic or inflammatory history were supportive of a developmental defect in this case series.
Various diagnostic imaging modalities were utilized in these dogs to determine the extent of association between the dacryops to the canaliculi and lacrimal sac. Dacryocystorhinography and subsequent intracyst injection of contrast with radiographs, CT scan, or MRI afforded better surgical planning and helped confirm patency of the normal nasolacrimal system and lack of communication between the dacryops and duct prior to surgery.
Dacryops do not typically spontaneously regress, and the natural course of a simple untreated dacryops tends to be chronic with no significant cyst enlargement.7 However, some dacyrops can become complicated by inflammation, fistulas, or malignant transformation.18,21 Enlargement may also lead to occlusion of the nasolacrimal duct and development of dacryocystitis.15 In this case series, surgical removal was curative. Laceration of inferior canaliculus occurred in all cases during surgery because of the close association between canaliculi and the cyst wall. Meticulous apposition of the tissue around the canalicular laceration and placement of an indwelling nasolacrimal catheter allowed adequate healing while preserving the patency of the nasolacrimal system. In the year following surgical excision, long-term success of the procedure was confirmed in all cases. Success was evidenced by a patent nasolacrimal system, resolution of epiphora, and excellent eyelid function and cosmesis.
Conclusion
In this case series, dacryops were documented and successfully treated in three young Labrador retrievers. This is the first report of dacryops in this breed. Dacryops were located within the inferior, medial eyelid and periocular tissue in all cases. Two of the cases had mild epiphora associated with functional nasolacrimal obstruction. Surgical excision of the cysts necessitated surgical incision with subsequent reconstruction of the inferior lacrimal canaliculus; the procedure was curative in all cases. Laceration of the nasolacrimal system (specifically the inferior canaliculus) is a potential complication associated with surgical excision of dacryops in this location. Diagnosis of dacryops was confirmed with histopathology and immunohistochemistry for smooth-muscle actin in all cases.
Acknowledgments
The authors thank the Indiana Animal Disease Diagnostic Laboratory at Purdue University for providing assistance with histopathology.
Tonopen-XL; Mentor O&O Inc., Norwell, MA 02061
Schirmer Tear Test Strips; Schering-Plough Animal Health Corporation, Union, NJ 07083-1982
Flor-I-Strip; Wyeth-Ayerst Laboratories, Philadelphia, PA 19101
Eye Wash solution; Major Pharmaceuticals, Livonia, MI 48150
Abbocath-T 24-gauge IV Cannula; Abbott Laboratories, Abbott Park, IL 60064-6408
Hypaque; Nycomed, Princeton, NJ 08540-6231
Red rubber urethral catheter, 3.5 French; Baxter-Allegiance Healthcare, McGaw Park, IL 60085
Vicryl Polygalactin 910 suture; Ethicon, Somerville, NJ 08876
Nurolon 4-0 braided nylon suture; Ethicon, Somerville, NJ 08876
Metacam meloxicam 1.5 mg/mL oral suspension; Merial, Duluth, GA 30096
Neomycin and polymyxin B sulfates and gramicidin ophthalmic solution USP; Bausch and Lomb Pharmaceuticals, Rochester, NY 14604-2701
Citation: Journal of the American Animal Hospital Association 45, 4; 10.5326/0450191
Citation: Journal of the American Animal Hospital Association 45, 4; 10.5326/0450191
Citation: Journal of the American Animal Hospital Association 45, 4; 10.5326/0450191
Citation: Journal of the American Animal Hospital Association 45, 4; 10.5326/0450191
Citation: Journal of the American Animal Hospital Association 45, 4; 10.5326/0450191
Citation: Journal of the American Animal Hospital Association 45, 4; 10.5326/0450191
Representative extraocular photographs of medial canthal masses on the left eye (OS) at initial presentation. (A) Case no. 1: a 1-year-old, castrated male Labrador retriever. (B) Case no. 2: a 10-month-old, spayed female Labrador retriever.
Computed tomography image of the left medial periocular area. Contrast from the dacryocystorhinogram and mass injection demarcates a normal nasolacrimal duct (red arrow) and independent, but closely juxtaposed, cystic mass (white arrow) at the medial canthus.
Intraoperative photograph of cyst dissection in case no. 1. The cystic mass has been partially dissected from the surrounding tissue and is being gently lifted from underlying associated connective tissue.
Histological photomicrograph of the dacryops. (A) Case no. 1; (B) case no. 2; (C) case no. 3. Hematoxylin and eosin stain.
Representative photographs of immunohistochemically stained cyst wall for smooth-muscle actin (case no. 2). Counterstained with hematoxylin and eosin.
(A) Photographs of immunohistochemically stained canaliculus for smooth-muscle actin with blood vessels, serving as a positive control. Canaliculus shows negative immunoreactivity for smooth-muscle actin. Counterstained with hematoxylin and eosin. (B) Photographs of immunohistochemically stained lacrimal glands and ducts for smooth-muscle actin. Counterstained with hematoxylin and eosin. The acinar cells and ducts are surrounded by numerous myoepithelial cells.
