Eye cancer, while rare, refers to the uncontrolled growth of abnormal cells that originate in or around the eye. Understanding its distinct forms is important for effective diagnosis and treatment.
Cancers Originating Within the Eye
Cancers that develop inside the eyeball are known as primary intraocular cancers. The most common type in adults is ocular melanoma, also called intraocular or uveal melanoma. This cancer originates from melanocytes, pigment-producing cells in the eye’s middle layer, the uvea. The uvea includes the iris, ciliary body, and choroid. Most uveal melanomas begin in the choroid, with fewer originating in the ciliary body or iris; iris melanomas tend to be slower-growing and less likely to spread.
Another type of primary intraocular cancer is retinoblastoma, which is the most common eye cancer found in children. This cancer starts in the retina, the light-sensing tissue at the back of the eye. Retinoblastoma can be hereditary, meaning it is passed down through families, or sporadic, occurring without a family history. The hereditary form often involves a mutation in the RB1 gene, a tumor suppressor gene, and typically affects both eyes, though it can manifest in one eye.
Primary intraocular lymphoma represents a rarer form of eye cancer that develops within the eye. This type is often a non-Hodgkin lymphoma. It frequently involves the vitreous and the retina. This condition is sometimes associated with lymphoma affecting the central nervous system.
Cancers Affecting Structures Around the Eye
Cancers affecting structures around the eye are often categorized as orbital or adnexal cancers. Eyelid cancers, for instance, are common, presenting as skin cancers like basal cell carcinoma, squamous cell carcinoma, and sebaceous gland carcinoma, often linked to sun exposure. Basal cell carcinoma is the most prevalent eyelid cancer and typically grows slowly without spreading. Squamous cell and sebaceous gland carcinomas are less common but can be more aggressive.
Orbital cancers are those that form within the orbit, the bony socket that houses the eyeball. These can include various types of tumors, such as lymphomas, which can affect the orbital tissues. In children, rhabdomyosarcoma, a soft tissue sarcoma, is the most common primary malignant orbital tumor. Other tumors like lacrimal gland tumors, affecting the tear-producing glands, can also occur in this region.
Cancers can also originate on the conjunctiva, the clear membrane covering the white part of the eye and lining the inside of the eyelids. Common types of conjunctival cancers include squamous cell carcinoma and melanoma of the conjunctiva. Squamous cell carcinoma of the conjunctiva usually appears as a reddish or white spot and is generally slow-growing, rarely spreading to other body parts. Conjunctival melanoma, though rare, can be more aggressive and has the potential to spread.
Cancers Spreading to the Eye
Cancer can spread to the eye from other parts of the body, a process known as metastasis, resulting in secondary eye cancer. These metastatic tumors are more common in adults than primary eye cancers. The eye’s rich blood supply allows cancer cells from distant organs to easily travel and establish new tumors.
The most frequent primary cancers that metastasize to the eye include breast cancer, which is the most common source in women, and lung cancer, most common in men. Other cancers that can spread to the eye include those originating from the prostate, kidney, and gastrointestinal tract. When cancer spreads to the eye, it most commonly affects the choroid, the vascular layer at the back of the eye, due to its extensive blood vessel network. While symptoms can vary, metastatic eye cancer can cause blurred vision or other visual disturbances.