A variety of neoplasms and related lesions can arise in the lacrimal gland (1,2,3,4,5,6,7,8,9,10,11,12,13). Lacrimal gland lesions have many similarities to those that occur in the major salivary glands. Lesions of the lacrimal gland can be broadly divided into epithelial and nonepithelial lesions. Nonepithelial lesions such as the lymphoid tumors, inflammations, and other neoplasms that affect the lacrimal gland are covered in other chapters. This chapter covers primary benign and malignant lesions derived from the epithelial structures of the lacrimal gland.

It is important to recall that the lacrimal gland is the only tissue in the orbit that normally contains epithelium and any primary epithelial tumor in the orbit has most likely originated in the lacrimal gland. However, metastatic epithelial neoplasms can reach the orbit by hematogenous spread from distant organs and secondary epithelial neoplasms can invade the orbit from adjacent structures, such as eyelid, conjunctiva, intraocular tissues, paranasal sinuses, and nasopharynx. On rare occasions, congenital ectopic lacrimal gland tissue in the orbit can give rise to cysts and neoplasms (12,13).

True primary epithelial lesions of the lacrimal gland can be divided further into benign and malignant categories. Benign epithelial lesions include ductal epithelial cyst (dacryops) and pleomorphic adenoma (benign mixed tumor). The latter is the only important primary benign epithelial neoplasm of the lacrimal gland. There are several malignant epithelial neoplasms of the lacrimal gland, the most important of which is adenoid cystic carcinoma (ACC). Other less common malignancies include pleomorphic adenocarcinoma (malignant mixed tumor), primary adenocarcinoma, mucoepidermoid carcinoma, primary squamous cell carcinoma, sebaceous carcinoma, acinic cell adenocarcinoma, ductal carcinoma, lymphoepithelial carcinoma, myoepithelial carcinoma, and cystadenocarcinoma. Most of these uncommon neoplasms were discussed in a recent comprehensive review of the subject (5).

Primary epithelial malignancies of the lacrimal gland (PEMLG) occur mostly in middle-aged adults; they are less common in the very young and the elderly. However, the important ACC seems to have a biphasic age distribution with some occurring in children in the first or second decade and another group occurring in young to middle-aged adults. There is no known predilection for race or gender.

Estimates regarding the incidence of lacrimal gland lesions vary from series to series depending on the source of the material and specifically which lesions were included in the survey. Rather than confusing the reader with those numbers, we attempted to make close estimates based on a comprehensive literature review. The following represents a fairly accurate and easy-to-recall average incidence of various lesions (5).

In the authors’ recent clinical series of 1,264 consecutive patients with orbital tumors from the Wills Eye Hospital Oncology Service, there were 114 (9%) lacrimal gland lesions. When dacryops (a cystic lesion) and other nonepithelial tumors were excluded, there were 30 solid primary epithelial tumors, of which 11 were pleomorphic adenoma and 19 were PEMLG. The 19 PEMLGs included 14 ACC (74%), 4 pleomorphic adenocarcinomas (21%), and 1 mucoepidermoid carcinoma (5%). That series, like most other studies, is biased in the sense that more difficult cases or malignant cases are likely to be referred to the Oncology Service. For example, several patients with ACC were referred for further management after incisional biopsy elsewhere disclosed the diagnosis. A completely excised pleomorphic adenoma would be less likely to prompt a referral to the Oncology Service.

Clinically, mass lesions in the lacrimal gland have consistent, but somewhat variable, features. Sizable solid lesions in the lacrimal gland fossa typically cause proptosis and inferior and nasal displacement of the globe. Benign epithelial tumors and lymphomas generally are painless, whereas malignant epithelial tumors and inflammations are more likely to cause pain. With imaging studies, benign tumors are more likely to show normal adjacent bone or smooth fossa formation. In general, malignant epithelial tumors are more likely to exhibit bone destruction as they progress. Clinical symptoms and signs and radiographic features are discussed in greater detail in the following sections.

Concerning prognosis, pleomorphic adenoma carries an excellent prognosis if the tumor can be completely removed within its capsule. Incomplete removal can lead to recurrence and eventual malignant transformation. Primary malignant epithelial tumors of the lacrimal gland are generally much more aggressive neoplasms with a relatively high incidence of local recurrence and distant metastasis despite aggressive treatment, often including orbital exenteration, irradiation, or chemotherapy. However, there is considerable variation in the degree of malignancy among the various malignant epithelial tumors (5).