When Should Patients With Acquired Nasolacrimal Duct Obstruction Be Imaged?
Thomas E.
Johnson,
MD
What are the possible causes of nasolacrimal duct obstruction? When should I worry about malignancy? What imaging options are available and which do you recommend?
Swelling over the lacrimal sac area usually represents a nasolacrimal duct obstruction with acute or chronic dacryocystitis. There are many causes of tearing, including blepharitis, trichiasis, distichiasis, eyelid malpositions, punctal stenosis, ectropion, dry eye syndrome, in addition to nasolacrimal duct stenosis and obstruction. Rarely, tumors involving the lacrimal sac fossa can present in this location (Figure 39-1). Most causes of tearing and lacrimal sac tumefaction are easily elucidated with a careful history and clinical examination. However, some patients also require imaging studies to further assess the area for a neoplastic process.
Figure 39-1. (A) A 61-year-old woman with right-sided lacrimal sac squamous cell carcinoma. Axial (B) and coronal (C) computed tomography without contrast reveals a large right-sided lacrimal sac tumor extending into the nasolacrimal duct.
Patients with primary acquired nasolacrimal duct obstruction present with symptoms of tearing, discharge, and sticking together of the eyelashes on awakening. If dacryocystitis develops, pain is usually noted. Historical features suggesting a lacrimal sac tumor may also include pain and recurrent dacryocystitis, but additionally may include bloody tears, a progressively growing mass in the lacrimal sac area, and a history of prior malignancy elsewhere in the body, especially lymphoma. Previous treatment for nasopharyngeal carcinoma is also concerning. On physical examination, clinical features suspicious for a lacrimal sac tumor include a firm mass in the lacrimal sac fossa extending above the level of the medial canthal tendon, blood extruding from the punctae, fixation of the mass to the skin, and cervical and preauricular lymphadenopathy in advanced cases. Lacrimal irrigation can reveal either a blocked or patent nasolacrimal duct. Examination of the nose can reveal an intranasal mass in advanced tumors.
A wide variety of epithelial and nonepithelial tumors, both benign and malignant, can arise from the lacrimal sac. Previous studies have shown that about 55% of lacrimal sac tumors are malignant, and the majority of malignant sac tumors are epithelial. Benign lesions include squamous and transitional cell papillomas, inverted papillomas, pleomorphic adenomas, and oncocytomas. The inverted papillomas can develop focally invasive carcinoma. The most common malignant neoplasms involving the lacrimal sac fossa include transitional cell carcinoma, squamous cell carcinoma, adenocarcinoma, adenoid cystic carcinoma, mucoepidermoid carcinoma, lymphoma, melanoma, metastatic tumors, and secondary tumors originating from the perinasal sinuses or overlying skin.
I find that the most useful imaging technique for evaluation of a lacrimal sac tumor is CT with contrast enhancement. The advantage of CT is its ability to assess bony changes associated with the tumor, because bony erosion can be evident. Vascular tumors will enhance with contrast. The studies also give an excellent view of the paranasal sinuses, because the maxillary sinus may be primarily or secondarily involved with the neoplasm. Lymphomas can be found in the lacrimal sac fossa, and these tumors usually mold to the surrounding structures without causing bony erosion. MRI is also useful for soft tissue analysis of the lacrimal sac, but does not image the bony structures as well as CT. However, T1- and T2-weighted images can help specify the soft tissue characteristics of the tumor and narrow the differential diagnosis.
Diagnostic echography (ultrasound) can also be a useful adjunct in lacrimal sac fossa evaluation. It is a rapid, noninvasive technique that may be available in the clinic. The normal lacrimal sac can be identified as a small, low reflective structure. Cases of dacryocystitis usually demonstrate a dilated sac that is very low reflective. A dacryolith can be viewed as a highly reflective echo-dense nodule within the dilated sac. Lacrimal sac tumors would be expected to exhibit similar echography characteristics to the similar tumors within the orbit.
Dacryocystography is radiographic visualization of the lacrimal sac and associated structures after injection of a contrast medium. After the application of topical anesthesia, the lower punctum is dilated and a small catheter is inserted and taped into position. A radiopaque contrast material is irrigated into the canaliculus, and imaging is performed using either plain x-rays or computerized digital subtraction methods. Blockage in the nasolacrimal duct can be visualized, as well as anatomical changes secondary to trauma, congenital anomalies, inflammatory diseases, fistulae, diverticula, previous surgery, or tumors. When a lacrimal sac tumor is present, uneven mottled densities may be noted within the lacrimal sac. Admittedly, with modern imaging this modality is rarely utilized.
Dacryoscintigraphy is a method where a drop of radionuclide tracer such as technetium-99m pertechnetate is instilled into the conjunctival cul-de-sac, and the lacrimal drainage system is imaged with a gamma-gram. It is most useful for detecting incomplete lacrimal system blocks and has the advantage of very low radiation exposure to the ocular lens. However, it is not very helpful in visualizing a lacrimal sac neoplasm.
Treatment of a lacrimal sac tumor depends on many factors, including tumor cell type, extent of the lesion, and condition of the patient. Malignant epithelial tumors can metastasize and be fatal. Treatment usually requires removal of the entire lacrimal drainage apparatus, including the lacrimal sac, canaliculi, and nasolacrimal duct with or without medial maxillectomy. Additionally, treatments include radiation therapy alone or postoperatively, radical surgery including orbital exenteration and sinusectomy when the tumor secondarily invades the orbit, and systemic chemotherapy and/or radiation therapy in patients with metastatic lesions.
In summary, lacrimal sac tumors are rare. Most cases of nasolacrimal duct obstruction can be diagnosed based on history and physical examination. Signs of a lacrimal sac tumor include bloody epiphora, a firm medial canthal swelling above the level of the medial canthal tendon, and history of prior malignancy. Although ultrasound is a rapid, noninvasive screening technique for lacrimal sac assessment, in my opinion CT scan provides the best imaging technique for suspected lacrimal sac tumors.
Suggested Reading
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