Iris Melanoma: NBEO and OKAP Review
Learn the NBEO and OKAP clues that distinguish iris melanoma from iris nevus, including documented growth, glaucoma and classic risk features.
Compared with choroidal melanoma, iris melanoma generally has which prognosis?
Iris Melanoma in 30 Seconds
Iris melanoma is the least common form of uveal melanoma and generally has the best prognosis, because it is often detected earlier than ciliary body or choroidal melanoma. It usually presents as a visible iris mass. For NBEO and OKAP, distinguish it from iris nevus by proving growth and identifying secondary complications.
Clinical Features
- Appearance: pigmented or amelanotic iris nodule, often inferior. Exam relevance: amelanotic lesions can still represent melanoma.
- Location: inferior iris involvement is common and has been hypothesized to relate to ultraviolet light exposure. Exam relevance: inferior location supports suspicion for melanoma.
- Growth: documented growth is the key sign favoring melanoma over nevus. Exam relevance: serial photography provides the decisive comparison.
- Secondary signs: corectopia, ectropion uveae, sectoral cataract, localized iris stromal atrophy or secondary glaucoma. Exam relevance: these findings suggest local tumor effects.
- Intrinsic vascularity may be present. Exam relevance: prominent vessels increase concern for melanoma.
Iris Nevus vs Melanoma
- Documented growth is the strongest feature favoring melanoma.
- Diameter greater than 3 mm or thickness greater than 1 mm increases suspicion for melanoma.
- Secondary glaucoma or hyphema favors melanoma.
- Pigment dispersion favors melanoma.
- Prominent intrinsic vascularity favors melanoma.
- The ABCDEF guide flags risk: Age 40 or younger, Blood (hyphema), Clock hour inferior, Diffuse configuration, Ectropion uveae and Feathery margins.
4 Facts Exams Always Ask
- Iris melanoma is the least common uveal melanoma and has the best prognosis.
- It favors the inferior iris, hypothesized to relate to ultraviolet exposure.
- Documented growth is the strongest clinical sign of malignancy.
- Observe small stable lesions. Treat growing or larger tumors with iridectomy or plaque radiotherapy. Reserve enucleation for diffuse or advanced disease.
The Classic Trap
The major board trap is calling a growing iris melanoma a benign iris nevus. Documented growth is the single most important sign. Secondary glaucoma, hyphema, pigment dispersion and a diameter over 3 mm or thickness over 1 mm support melanoma. Iris melanoma usually has a better prognosis than ciliary body and choroidal melanoma. Ultrasound biomicroscopy is useful for measuring tumor thickness and detecting ciliary body extension.
Clinical Pearl
Iris melanoma has the best prognosis among uveal melanomas because clinicians can see it earlier and tumors are often smaller at diagnosis. Serial photography should drive decisions, since documented growth matters most. Fine-needle aspiration biopsy is rarely required because the diagnosis is usually clinical. Diffuse iris melanoma can present with acquired hyperchromic heterochromia and unilateral glaucoma, a classic NBEO and OKAP presentation.
Checkpoint 1
Which clinical setting should raise suspicion for iris melanoma rather than a simple iris nevus?
Checkpoint 2
Which imaging modality is especially helpful for evaluating posterior extension of an iris lesion into the ciliary body?
A patient has a pigmented lesion in the inferior iris. Serial slit-lamp photographs show clear enlargement over follow-up. The eye also develops mild corectopia and elevated intraocular pressure. Which finding most strongly favors iris melanoma over a benign iris nevus?
Which finding in a pigmented iris lesion most strongly favors melanoma rather than iris nevus?
Sources & Publisher Info
References
- American Academy of Ophthalmology. Basic and Clinical Science Course, Section 4: Ophthalmic Pathology and Intraocular Tumors.
- Shields CL, Shields JA. Clinical Ocular Oncology.
- American Academy of Ophthalmology. EyeWiki: Iris Melanoma.
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