In spite of being a small organ, the eyelids contain numerous histological elements that can be the origin of benign and malignant lesions.
The eyelids are composed of four layers: Skin and subcutaneous tissue, striated muscle (orbicularis oculi), tarsus, and conjunctiva.
Orbital tumors can be benign or malignant and arise primarily within the orbit or secondarily from an adjacent source, such as the eyelid, paranasal sinus, or intracranial compartment. Orbital tumors can also be metastatic from distant sites.
Some types of orbital tumors usually cause proptosis and displacement of the globe in a direction opposite the tumor. Pain, diplopia, and vision loss may also be present. The diagnosis of orbital tumors is suspected based on the history, examination, and neuroimaging (CT, MRI, or both), but confirmation often ultimately requires a biopsy. Causes and treatment vary by age group.
Conjunctival melanocytic lesions are the most common tumors of the conjunctiva, comprising 52% of all conjunctival tumors. Several classifications have been suggested for conjunctival melanocytic lesions. Thus far, the 1980 World Health Organization (WHO) classification has been most widely used and includes three pathologic categories: conjunctival nevus, conjunctival melanosis, and malignant melanoma (MM).