First off: what is cancer? Cancer is a group of diseases characterized by uncontrolled cell division. These dividing cells may form tumors. Malignant tumors are cancerous; they can invade nearby tissue. Cancer originates in one place and can spread to other parts of the body. The term for this spread is metastasis. The National Cancer Institute has a great, easy-to-understand overview of cancer here. According to the Center for Disease Control (CDC) and the American Cancer Society (ACS), the most common cancers in the US are breast, prostate, and lung (1, 2).
 |
| From ACS |
In terms of ocular cancer, there are various sites within and around the eye that cancerous tumors can be found. We'll go through some of the major types in each category.
1. INTRAOCULAR [within the eye]
- Primary intraocular cancers are cancers that originate in the eyeball.
- Retinoblastoma is the most common eye cancer in children, accounting for 3% of all childhood cancers. This rare cancer can be non-inherited or inherited via a mutation in the RB1 gene, which is also linked to an increased risk of osteosarcoma (bone cancer). All babies are screened at birth, but this may not be present at birth. That's why it is crucial to not only see your pediatrician for well-baby exams but to ALSO see your eye doctor (for more info on infant eye exams, read the InfantSEE post). Early diagnosis is key! The most common signs of retinoblastoma are a white pupillary reflex (instead of the normal red reflex that you often see when you take a flash photo) called leukocoria, and eye turns (strabismus) (3).
 |
| Leukocoria from retinoblastoma, image: University of Michigan |
- Uveal melanoma is the most common primary intraocular malignancy in adults. It forms in the eye's melanocytes, the cells that make pigment (melanin). [The uvea is the pigmented middle layer of the eye and includes the iris, ciliary body, and choroid. The choroid is the vascular tissue that lies between the retina (the light sensitive tissue that lines the back of the eye) and the sclera (the white part of the eye).] Choroidal melanomas account for 80% of all uveal melanomas, affecting six out of every one million Americans (4). Choroidal melanomas most often have no symptoms and are found during routine eye examination. Choroidal melanomas can metastasize, to the liver most commonly, also occasionally to the lungs, bone, skin, and brain (Kanski, 7th ed).
- Primary intraocular lymphoma (PIOL) often presents in the elderly and immunocompromised, with possible symptoms of floaters, blurred vision, redness, and/or sensitivity to light. Lymphoma is a cancer of the lymphatic system, the system that helps protect the body from infection. Lymphoma is classified as either Hodgkins or non-Hodgkins. Non-Hodgkins lymphoma can be further categorized based on what type of cells are involved. Most are B-cell. Because lymph tissue is found throughout the body, lymphoma can begin nearly anywhere. Lymphomas can occur intraocularly but also can occur in other structures on/around the eye (more on that later). PIOL is primarily non-Hodgkins, B cell lymphoma, and is highly correlated with primary central nervous system lymphoma (PCNSL). In fact, up to 80% of patients with PIOL will be subsequently diagnosed with brain lymphoma (5).
- Secondary intraocular, or metastatic, cancer is cancer that originates elsewhere in the body and spreads to the eye. Secondary intraocular cancer occurs more often than primary. The most common cancers to spread to the eye are breast and lung, and the most common place for them to spread within the eye is the vascular choroid. One study found that 34% of those eyes diagnosed with uveal metastasis did not have a history of cancer at the time of diagnosis. Further evaluation of that 34% revealed over a third of them had a primary tumor in the lungs (6). According to Wills Eye Hospital, about 25% of patients who present to the eye doctor with eye metastasis have no known history of systemic cancer and are later found to have a cancer in the body (7). Key point: the detection of cancer in the eye can precede the diagnosis of cancer elsewhere in the body, especially in the case of lung cancer.
 |
| Choroidal melanoma, image: ECN |
- Conjunctival squamous carcinoma occurs most often in older white males, and is linked to UV exposure. This rarely spreads to distant sites but can spread locally behind the eye and in the orbit (8).
- Conjunctival melanoma appears as a pigmented area on the white part of the eye. It can arise from an existing nevus/mole or from a precancerous condition called primary acquired melanosis (PAM). Unlike a squamous carcinoma, there is a risk of spread to the lymph nodes and other organs (9).
- Conjunctival lymphoma presents as a salmon-colored patch, often found under the eyelids, most commonly in late adulthood. In about 20% of cases, lymphomas in other parts of the body are found (10).
 |
| Conjunctival lymphoma, image: Wills Eye |
3. EYELIDS [The Skin Cancer Foundation reports that eyelid skin cancer accounts for 5-10% of all cases of skin cancer.]
- Basal cell carcinoma (BCC) is by far the most common eyelid tumor, accounting for about 90% of eyelid cancers. Most occur on the lower lid, and are found more commonly in older, fair-skinned people with chronic exposure to UV radiation. BCC is locally invasive but does not metastasize (Kanski, 7th ed).
- Squamous cell carcinoma (SCC) is similar to BCC in that it's typically found on the lower lid of older, fair-skinned patients with chronic exposure to UV radiation. It is less common than BCC, but more aggressive, and metastasis to nearby lymph nodes occurs in 20% of cases (Kanski, 7th ed).
- Melanoma accounts for less than 1% of eyelid cancers. Melanomas are aggressive and potentially life-threatening. They are typically pigmented, but sometimes not. Melanomas can look like moles (nevi), or can arise from moles. The ABCs of melanomas point out characteristics of malignant melanomas that are usually not present with benign moles:
- Asymmetry
- Border (uneven or irregular)
- Color (non-uniform, variety of colors or shades)
- Diameter (bigger is not better)
- Evolution (change over time)
- Sebaceous gland carcinoma (SGC) is a malignant cancer arising from the oil glands in the eyelids. It typically presents as a painless bump on the upper lid, and can be difficult to diagnose. Sebaceous carcinoma is found more frequently in females than males, and is more common in the elderly (Kanski, 7th ed). It can metastasize to lymph nodes and other organs (11).
- Merkel cell carcinoma (MCC) is a rare form of skin cancer that grows quickly and metastasizes early. It appears as a raised, red-violet bump on the skin, typically linked to chronic sun exposure. MCC is most common in elderly caucasians (12).
 |
| BCC, image: Wills Eye |
 |
| MCC, image: pubmed |
4. ORBIT [the eye socket, including bones, muscles, nerves, and the lacrimal glands (the almond-shaped glands that secrete tears)]
- Lacrimal gland lymphoma accounts for over a third of all malignancies of the lacrimal gland, predominantly affecting elderly women (15). It was found that one to two-thirds of patients develop systemic disease (if not already present at the time of orbital biopsy), usually within 2.5 years of orbital biopsy (16).
- Adenoid cystic carcinoma of the lacrimal gland is the most common malignant epithelial tumor of the lacrimal gland. Occurring most often between the ages of 40 and 60, adenoid cystic carcinoma causes the eye to be displaced downward, and can also cause pain as it spreads to the nearby nerves and bone (17,18).
 |
| CT of an adenoid cystic carcinoma of the lacrimal gland, image: ECN |
- Malignant mixed tumor of the lacrimal gland is the second most common malignant tumor of the lacrimal gland. It occurs most often in the elderly. It can appear without a history of lacrimal mass, or it can arise from a prior benign mass that was incompletely excised or a long-standing mass that suddenly increases in size (19. 20).
5. BRAIN
Why do I include this in our conversation? Because the eyes are an extension of the brain, and some brain tumors can be detected during an eye examination. I plan to do a separate blog post about it, but in short, visual field exams can help detect and even localize some masses in the brain.
CliffsNotes: Cancer can start in and around the eye, or it can spread to the eye from elsewhere in the body. It often doesn't have symptoms, so be sure to get your yearly dilated eye exam whether you have a history of cancer or not!
Additional recommended resources:
No comments:
Post a Comment