Imaging of the Lacrimal Gland

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The lacrimal gland is situated superolateral to the eye and produces tears that moisten, lubricate, and protect the delicate corneal and conjunctival epithelium. Anatomically related to the orbit but embryologically and functionally more closely related to the salivary glands, radiological imaging has proven invaluable in delineation and differentiation of the unique range of pathological processes affecting the lacrimal gland. This article details traditional and new imaging techniques used in investigating such pathology and discusses the imaging findings and patterns of spread characteristic of various neoplastic, inflammatory, and structural processes ranging from benign adenomas, adenocarcinomas, and lymphomas to sarcoidosis, Mickulicz’s syndrome, histiocytosis, and benign dacrocysts.

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Structure and Function of the Normal Lacrimal Gland

The lacrimal gland is a serous gland, bi-lobed in shape, and measuring approximately 20 × 12 × 5 mm. While somewhat variable in size between individuals, differences between the normally symmetrical right and left glands provide an important clue to the presence of pathology. The larger orbital lobe is situated posteriorly and superiorly within a shallow bony fossa indenting the inferior surface of the supraorbital margin of the frontal bone, while the smaller palpebral lobe is situated more

Imaging of the Lacrimal Gland

Ultrasound (US), CT, and MRI are all used in imaging of the lacrimal gland. As in most situations, imaging is invaluable in (i) confirming whether the lesion lies within the lacrimal gland or within any of the other orbital structures where it would be likely to present clinically in the same way; (ii) defining the nature and extent of the lesion for diagnosis and surgical planning; and (iii) monitoring progress over time and the effectiveness of treatment.

Tumors of the Lacrimal Gland

About 10% of space-occupying lesions of the orbit arise from within the lacrimal gland.8 Lacrimal neoplasms arise from all the structures related to the gland and its function, namely its aqueous (and also sebaceous) secretory epithelial tissue, its lymphoid tissue, and its nervous and vascular tissue. The full range of degrees of malignancy is also represented. Assessing the relative incidence of various lacrimal tumors and other lacrimal masses such as dacrocysts has been difficult. Table 1

Epithelial Tumors of the Lacrimal Gland

Primary tumors deriving from epithelial tissue are relatively common with recent reports suggesting that they account for approximately 20% of all solid lacrimal gland masses.8

Clinical presentation is typically with proptosis and inferior and medial displacement of the eye. More rapidly growing tumors are more likely to present with diplopia as there is less time for compensation. While malignant lesions may present with symptoms of pain, and the perineural involvement of adenoid cystic

Neural Tumors

Derived from the neural tissue of the lacrimal gland and neighboring structures, localized neurofibromas may occur within the lacrimal fossa. They can be difficult to differentiate on their radiological appearances from a pleomorphic adenoma since they are also well-circumscribed, usually homogenous masses that are isodense to extraocular muscle on CT and may likewise excavate the lacrimal fossa.31, 32 Lacrimal neurofibromas are associated with systemic neurofibromatosis in 12% of cases. They

Metastases

Metastases may rarely occur to the lacrimal gland and their imaging appearances are similar to those of primary tumors.33 Additionally, there may be lacrimal spread of metastatic tumor from neighboring orbital soft tissue or bony structures. Carcinoma of the breast most commonly metastasizes to the soft tissue, whereas prostatic carcinoma results in bony metastases. Melanoma may spread either to soft tissue or to bone. Renal and thyroid metastases produce osteolytic bony lesions. In children,

Other Tumors

Primary squamous cell carcinoma and sebaceous carcinoma may arise from the lacrimal gland, due to the presence of heterotopic tissue.8 More typically, such tumors may spread from the upper eyelid, or in the case of sebaceous carcinoma, from the meibomian glands of the tarsus or the sebaceous glands of the eyelashes and brow hairs. Their appearances are typical of malignant lacrimal tumors—a soft-tissue mass with bony erosion. Early radiological diagnosis of such lesions dramatically affects

Infection of the Lacrimal Gland

Like most epithelial structures in contact with the outside, acute infection (dacryoadenitis) may occur from bacterial or viral infection. The condition is normally unilateral and usually occurs in children and young adults. A smooth swelling will be seen on imaging and enlargement of other structures such as lymph nodes may be visualized.37 Care must be taken to determine any orbital, cavernous, or intracranial extension or associated venous sinus thrombosis. Chronic dacryoadenitis may result

Dermoid Cysts

Dermoid cysts are thought to arise from ectodermal rests, separated off at suture lines, and are therefore developmental choristomas. They may be superficial or deep and often have histological features of rupture (50%); less commonly this is manifested clinically with low-grade inflammatory features. On imaging, they are usually associated with adjacent bony change and localized excavation of bone. They may show calcification. Frontozygomatic dermoids may be difficult to differentiate from

Inflammatory and Granulomatous Pathology of the Lacrimal Gland

Inflammatory lacrimal disease is the second most common inflammatory disease of the orbit (after orbital myositis).16 Clinical presentation is characterized by pain and a tender palpable lacrimal gland. Approximately 50% of cases are associated with a systemic condition such as sarcoidosis, Sjogren’s syndrome, Wegener’s granulomatosis, or other autoimmune conditions.

Inflammatory conditions of the lacrimal gland are characterized radiologically by diffuse unilateral or bilateral enlargement with

Lacrimal Ductal Cysts (Dacrocysts or Dacryops)

Lacrimal ductal cysts develop mainly within the palpebral lobe of the gland where the tear ducts emerge on to the conjunctiva. They typically manifest as a slow-growing painless mass in the region of the external canthus that causes cosmetic problems. Sometimes they may result in a dry eye as many of the neighboring ducts become secondarily compressed. The pathogenesis is thought to relate to trauma or inflammation, weakening the ductal walls, allowing ductal dilatation. Their cystic nature is

Conclusions

The myriad of pathologies of the lacrimal gland, reflecting its site, function, and developmental link with the salivary glands, present particular diagnostic challenges for imaging. The mainstays of such imaging are CT and MRI. Due to the bony relations of the gland and the presence of calcification within some lesions, the latter complements rather than supersedes the former. As benign and malignant epithelial pathology may be indistinguishable on imaging, excision of the whole gland at the

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