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Most are probably congenital in origin while others may be acquired. The epithelial lining of these cysts can be squamous or ciliated-respiratory in type, depending on the region of the sac lining that spawns the lesion. Conjunctival cysts arising from the medial regions of the forniceal conjunctiva must be distinguished from cysts deriving from the lacrimal sac. Other cyst-like conditions may be formed by closure of a dacryocystocele as a result of trauma or inflammation.
(A dacryocystocele is a diverticulum, a saccular outpouching of an epithelial-lined cavity, often resulting from an obstruction and attendant increased intraluminal pressure.) A lacrimal sac cyst presents as a gradually enlarging inner canthal mass characterized by a soft, fluctuant, and irreducible nontender cystic structure. Surgical excision of the adherent cyst may produce a tear in the sac wall, which should be repaired intraoperatively. A conjunctival cyst may also produce external medial canthal swelling but be visible in the forniceal subconjunctival tissues. The authors illustrate herein the first immunohistochemical analysis of a cyst that displayed respiratory-type epithelium and explore 2 possibilities: a lacrimal sac origin or a choristomatous cyst of paranasal sinus origin.
A 54-year-old female with a history of breast cancer in remission described the painless enlargement of a right lower eyelid mass for over 10 years, with acceleration in the preceding few months. She denied tearing, discharge, or antecedent local trauma. On ophthalmologic examination, best corrected visual acuity was 20/40 bilaterally. A nontender 2 × 2 cm soft mass was palpable in the right lacrimal sac region. Digital massage produced no discharge, and punctal probing and irrigation demonstrated patency of the lacrimal system.
Magnetic resonance imaging of the face and orbits demonstrated a 1.9 × 1.6 cm mass near the lacrimal sac abutting, but not deforming, the inferomedial margin of the right globe. T2-weighted gadolinium contrast studies showed enhancement of the cyst lumen and also the lumen of a separate small lacrimal sac (Fig. 1, top left). The bright images reflect the mucinous contents of the cyst and sac and are iso-intense with the mucinous contents of the vitreous cavities. Dacryocystography was not performed.
Fig. 1(Top, left) Magnetic resonance imaging with contrast, T2-weighted images. Upper panel shows coronal plane with enhancing cyst (c) and separate lacrimal sac (arrow). Lower panel shows enhancing cyst in the axial plane. (Top, right) Intraoperative view of cyst (arrow) and adherent lacrimal sac (arrowhead). (Center, left) Low power view of bicameral cyst (c). (hematoxylin and eosin, × 1). (Center, right) Double-layered epithelial cyst lining with goblet cells and pseudodecapitation secretion. (hematoxylin and eosin, × 400). (Bottom, left) Phosphotungstic acid–hematoxylin (PTAH) stain highlights fine apical cilia (arrows). (PTAH, × 400). (Bottom, right) Periodic acid–Schiff (PAS) stain is positive in the goblet cells of the cyst lining (PAS, × 400).
Surgical exploration and excision of the cyst was achieved via a transcutaneous approach. Bicanalicular silicone stents were placed in the upper and lower puncta and retrieved in the nose, confirming patency of the nasolacrimal duct. The lesion was encountered immediately deep to the orbicularis oculi muscle plane (Fig. 1, top right), and its anterior margin was easily dissected from the muscle. The posterior portion of the cyst was found to be fused with the anterior wall of the lacrimal sac. Saline and methylene blue dye irrigated freely through the nasolacrimal system without resistance, staining, or accumulation within the cyst. Rupture of the cyst yielded an oily material that was free of methylene blue. The rent in the lacrimal sac was repaired with absorbable sutures. The stents were left in place and tied off beneath the inferior nasal turbinate. The postoperative course was uneventful without epiphora. Punctal irrigation verified patency of the lacrimal system. Computed tomography of the face and orbits 2 weeks postoperatively confirmed complete excision of the lesion.
Retrieved from formalin was a rubbery piece of tissue measuring approximately 1.7 × 1.5 × 0.7 cm. On bisecting the tissue a partially collapsed cyst containing clear fluid was encountered. Histopathologic examination revealed an empty cyst lined by bilayered epithelium with pseudodecapitation secretion and numerous periodic acid–Schiff-positive goblet cells. A phosphotungstic acid-hematoxylin stain disclosed multiple apical cilia (Fig. 1). Neither inflammation nor squamous metaplasia was present. Immunoperoxidase stains showed positivity for cytokeratin (CK) 7 (full lining thickness), CK17 (basilar layer only), and CK18 (suprabasilar layer only). Additionally, the epithelial lining stained positively for epithelial membrane antigen (EMA) and low molecular weight CK (CAM 5.2) (Fig. 2).
Fig. 2Immunohistochemistry. (Top, left) Cytokeratin-17 is positive in basilar epithelial layer of cyst lining. Note empty cyst lumen (L). (Top, right) Cytokeratin-18 is positive only in suprabasilar epithelial layer. (Center, left) Cytokeratin-7 stains full thickness of epithelial lining. (Center, right) CAM 5.2 is positive in epithelial lining. (Lower, left) EMA stains the epithelial lining. (All panels: immunoperoxidase stain, diaminobenzidine chromogen, × 400.)
The mid-to-lower regions of the lacrimal sac are lined by pseudostratified columnar epithelium, including goblet cells and, in areas, display apical cilia, as in the current case.
Intraluminal pressure may cause compression of the lining cells, producing appearance of a double layer of cuboidal epithelium. The only immunohistologic study of normal lacrimal sac to date showed positivity for 34 beta E12, CAM 5.2, EMA, and CK7, the latter 3 mirroring the findings in the current case.
No studies of the normal lacrimal sac to date have been studied with CK17 and 18.
Although the attachment of the cyst to the sac in the current case was described precisely by the surgeon (posterior cyst wall to anterior sac wall, well below the medical canthal tendon), other reports lack such specificity. One report
notes the cyst's position beneath the medial canthal tendon with a connection to the sac “near the point of entry into the nose.” Location below the medial canthal tendon is important as malignancies of the lacrimal sac often occur above the tendon.
The histopathologic differential diagnosis in the current case is headed by an ectopic, choristomatous respiratory cyst. Although the constellation of histopathologic findings herein is identical to that of respiratory cysts,
the authors favour the diagnosis of lacrimal sac cyst considering its attachment to the lacrimal sac wall and believe it was congenital, arising from an embryonic ectopia of lacrimal sac epithelium. The lack of squamous metaplasia and inflammation (illustrated elsewhere)
lessens the likelihood of origin from a secondary closure of a dacryocystocele. (Both congenital and acquired dacryocystoceles commonly show histopathologic evidence of chronic inflammation and infection).
A second possibility suggests an origin from a displaced anlage of sinus respiratory epithelium that created a choristomatous lesion. A previously reported upper eyelid respiratory cyst that was unattached to and distant from the lacrimal sac, presenting above the medial canthal tendon, illustrates such an option.
A congenital canalicular cyst is a unique entity occurring in the lacrimal drainage system. Lined by multilaminar nonkeratinizing squamous epithelium, it is easily distinguished from the bilayered lacrimal sac cyst. Canalicular cysts share the immunohistopathologic profile of the normal canaliculus and canaliculops (CK7 and 18+ in superficial cells, CK14+ in basal and suprabasal cells, CK17 patchily + throughout).
Canaliculops (canaliculocele, canalicular diverticulum) differs from canalicular cysts in that that the former entity represents an ectasia of a segment of the canaliculus rather than a sacculated cyst isolated from but adjacent to the lacrimal drainage system.
Despite the small territory subsumed by the term medial canthal region, there is a rich spectrum of developmental, cystic, inflammatory, obstructive, and neoplastic conditions that can arise within the region. One must carefully distinguish between lesions of the canaliculi and those of the lacrimal sac and upper nasolacrimal duct. Furthermore, diverticula and total segregated cysts may present in any location (anterior, inferior, posterior, lateral) relative to the basic anatomic structure.
Footnotes and Disclosure
The authors have no proprietary or commercial interest in any materials discussed in this article.
References
System of Ophthalmology. XIII, part 2. CV Mosby,
St Louis1974: 733-735
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