Benign iris tumors: types and symptoms

Benign iris tumors are a heterogeneous group of formations composed of melanocytes, smooth muscle cells, nerve sheath, and blood vessels, as well as cystic lesions. Most of these lesions are asymptomatic and are detected incidentally with a slit lamp. The danger lies not so much in their malignancy as in complications (secondary glaucoma, hypema, pupillary deformity) and the rare but real possibility of some nevi transforming into iris melanoma. According to observations by ophthalmology oncology centers, the growth of iris nevus into melanoma has been observed in approximately 8% of patients over 15 years, and there are clear clinical risk factors (the ABCDEF mnemonic). [1]

Melanocytic lesions (iris nevus, melanocytoma) and cysts (primary epithelial and stromal, secondary) are most common. Less common are benign tumors of smooth muscle (leiomyoma), nerve sheath (schwannoma/neurofibroma), vascular anomalies (microhemangioma/racemosa hemangioma), and juvenile xanthogranuloma in childhood. Management varies from observation and photographic documentation to local resection or targeted brachytherapy; the choice depends on growth, anterior chamber angle involvement, and glaucoma risk. [2]

Anterior segment imaging—angular gonioscopy, anterior segment optical coherence tomography, and ultrasound biomicroscopy—defines today's standard: safe, noninvasive, and repeatable. Ultrasound biomicroscopy is better at "seeing" deep and iridociliary components, while optical tomography is more sensitive to fine, superficial lesions; these methods complement each other. [3]

Table 1. The main benign formations of the iris and their “hint” signs

Group	Examples	Clinical clues
Melanocytic	Nevus of the iris, melanocytoma	Pigmented nodule, possible feathery edges (risk), ectropion uvea
Cysts	Primary (epithelial/stromal), secondary	Thin-walled formation with a lumen; more often observed
Neuromeningeal	Schwannoma, neurofibroma (including neurofibromatosis type 1)	Pale/amelanotic node, "nervous" history
Smooth muscle	Leiomyoma	A non-pigmented, slow-growing mass that may mimic melanoma
Vascular	Microhemangioma, racemosa hemangioma	Recurrent hypema, telangiectasias on the iris
Histiocytic	Juvenile xantagranuloma	In infants; hypema + secondary glaucoma

Code according to ICD-10 and ICD-11

In the ICD-10-CM (clinical modification, USA), benign tumors of the iris are coded in the "iris and ciliary body" block: D31.41 (right), D31.42 (left), D31.40 (unspecified). In the "basic" ICD-10 WHO, the D31.4 "ciliary body" category is often used for the iris/ciliary body without specifying the side. [4]

ICD-11 provides a separate entry “2F36.1 Benign neoplasm of iris” within the block “benign neoplasms of the eye and its appendages” (2F36), with the possibility of post-coordination of lateralization. [5]

Table 2. Code correspondence

Classification	Code	Description
ICD-10-CM	D31.41 / D31.42 / D31.40	Benign neoplasm of iris and ciliary body: right/left/unspecified side. [6]
ICD-10 (main)	D31.4	Benign neoplasm of the ciliary body (in some registries includes the iris). [7]
ICD-11 MMS	2F36.1	Benign neoplasm of iris (with side modifiers). [8]

Epidemiology

True population-based registries of benign iris tumors are few: most data are from clinical series. In a large clinical-epidemiological study conducted in 2025, the incidence of iris nevi in the general Spanish population was approximately 4.8%, meaning nearly one in twenty adults has at least one iris nevus. Most of these remain stable and do not require intervention. [9]

Iris cysts are a relatively common finding among all iris lesions, but population-based estimates are scarce. In a series of 3,690 iris lesions, cysts accounted for approximately 21%, with 87% of these being iris pigment epithelial cysts; primary stromal cysts were more common in children.[10]

Benign tumors of "rare" lineages—leiomyomas, schwannomas, and neurofibromas—are described in isolated case series and clinical observations; their frequency is orders of magnitude lower than that of nevi and cysts. The prevalence can only be estimated based on the total proportion of "solid nonpigmented" lesions in ophthalmic oncology registries. [11]

The risk of iris nevus transformation into melanoma is low, but not zero. According to the Shields Center, among 1,611 referred nevi, melanoma development was observed in 8% over 15 years; risk factors "ABCDEF" (see below) have been identified, which helps stratify surveillance. [12]

Table 3. Epidemiological landmarks

Indicator	Meaning
Prevalence of iris nevi	≈4.8% in the general population (Spanish cohort, 2025). [13]
The proportion of cysts among iris lesions	≈21% (large series), 87% - pigment epithelial cysts. [14]
Risk of nevus developing into melanoma	≈8% over 15 years in a directional sample; tied to ABCDEF factors. [15]

Reasons

• The reasons depend on histogenesis.
• Melanocytic lesions (nevus, melanocytoma) are focal proliferations of iris melanocytes; melanocytoma is a dense pigmented variant with possible necrosis-induced pigment dispersion and an increase in intraocular pressure. [16]
• Cysts - primary (epithelial/stromal) and secondary (after injury/surgery, epithelial ingrowth). Primary ones are more often idiopathic. [17]
• Neuromeningeal tumors (schwannoma, neurofibroma) arise from Schwann cells/peripheral nerves; in neurofibromatosis type 1, multiple hamartomas (Lisch nodes) are possible. [18]
• Leiomyoma is a benign tumor of the smooth muscle of the iris/ciliary body that clinically mimics non-pigmented melanoma.[19]
• In vascular anomalies (microhemangioma, racemose), the leading mechanism is the congenital features of the vascular network of the iris. [20]

Risk factors

Light-colored irises and European descent are associated with a higher incidence of pigmented lesions and uveal tumors in general. The presence of oculodermal melanosis/ocular melanosis increases the likelihood of uveal tumors, so close monitoring is recommended in such patients. Neurofibromatosis type 1 is associated with Lisch nodules and neurofibromas. [21]

The clinical factors "ABCDEF" have been validated for the development of nevus into melanoma: Age (young age), Blood (hypema), Clock hour (inferior localization), Diffuse (diffuse type), Ectropion uveae (ectropion), Feathery margin (feathery margins). The presence of several points is a reason to activate the tactics. [22]

Pathogenesis

Melanocytic lesions represent a benign clonal proliferation of melanocytes; melanocytomas may undergo spontaneous necrosis and pigment seeding into the trabecular meshwork, leading to increased pressure (secondary glaucoma). Cysts are formed from iris epithelium (pigment or stroma) or from epithelial infiltration following surgery/injury. [23]

Neuromeningeal and smooth muscle tumors grow slowly, remaining stable for years; the clinical problem is more often related to mechanics (pupil deformity, angle block, cataract) than to aggression. Vascular anomalies can lead to recurrent hyperemas even with a small lesion. [24]

Symptoms

Most often, there are no complaints and the incidental discovery of a "spot" on the iris. Cosmetic asymmetry, pigment "spreading," pupil deformation (corectopia), and uvea ectropion are possible. If the angle is involved, signs of secondary glaucoma (halos, pain, nausea) are present. With vascular lesions and juvenile xanthogranuloma, episodes of spontaneous hypema are observed. [25]

Table 4. Symptoms and probable types

Symptom/sign	Probable types
Pigmented nodule without growth	Nevus of the iris
A very dark "velvety" node, with time ↑IOP	Melanoma
Thin-walled cavity, translucency	Cyst (usually epithelial)
Recurrent hypema	Vascular anomaly, juvenile xanthogranuloma (in children)
Feather-like edges, ectropion, diffuseness	Risk of nevus growth → melanoma (ABCDEF)

Classification, forms and stages

• Formal "TNM staging" is not used for benign tumors. In practice, a morphological classification is used:
• melanocytic (nevus, melanocytoma),
• cysts (primary: epithelial/stromal; secondary),
• neurogenic (schwannoma/neurofibroma),
• smooth muscle (leiomyoma),
• vascular (microhemangioma, racemose),
• histiocytic (juvenile xanthogranuloma). [26]

Separately, “pseudotumors” of the iris (pigment dispersion, drug pigmentation) are distinguished, which imitate the volumetric process, but are treated differently. [27]

Complications and consequences

Key complications include secondary glaucoma (angle block, pigment seeding, synechiae), hypema, progressive pupillary deformity, photophobia, and glare (after extensive resections). With melanocytoma, the risk of increased intraocular pressure increases significantly with long-term observation. Although rare, transformation of some nevi into melanoma is possible; isolated cases of malignancy have been described in melanocytoma. [28]

When to see a doctor

Urgent - for an episode of "blood in the eye" (hypema), painful/"stony" eye, iris rings, sudden pupil deformity, or a new, rapidly growing iris spot. Elective - for any new iris finding: baseline photographic documentation and measurements are required before further observation. Children with suspected juvenile xanthogranuloma require prompt evaluation due to the risk of glaucoma. [29]

Diagnostics

1. Slit lamp examination + photography. We record the size, shape, color, vascularity, and presence of ectropion/corectopia. A "current vs. previous visit" comparison is the main criterion for activity. [30]
2. Gonioscopy. We look for "sowing" in the angle, adhesions, and iridocorneal changes - this changes the tactics (diffuse/angular forms are treated more actively). [31]
3. Anterior segment OCT (AS-OCT) provides excellent visualization of thin superficial and amelanotic lesions and helps differentiate solid nodules from cysts. [32]
4. Ultrasound biomicroscopy (UBM) is the best technique for deep, pigmented, and iridocyliary components; it shows the thickness and relationship to the ciliary body. [33]
5. Additionally, as indicated. OCTA of the anterior segment - for vascular anomalies; measurement of intraocular pressure; sometimes - fine-needle biopsy (rarely) in case of doubt and to exclude melanoma or for molecular verification of rare tumors (taking into account the risk of "seeding"). [34]

Table 5. What does this or that visualization provide?

Method	Strengths	When is it mandatory?
Slit lamp + photo	Cheap, fast, repeatable	For everyone - for the baseline
Gonioscopy	Angle/"seeding", synechiae	If angle involvement is suspected
AS-OCT	Subtle foci, cysts, borders	For amelanotic and cystic lesions
UBM	Depth, iridociliary component	For pigmented/deep/thick nodes
OKTA (front segment)	Non-violent "angiography"	Suspected vascular anomaly

Differential diagnosis

• It is necessary to distinguish:
• Iris nevus vs. iris melanoma: growth, feathery edges, uvea ectropion, hypema, and diffuse configuration favor melanoma (ABCDEF). UBM/AS-OCT helps assess thickness and ciliary phase. [35]
• Cyst vs. solid nodule: AS-OCT shows the cyst lumen and thin wall; UBM confirms the cavity and tissue connection.[36]
• Melanocytoma vs. melanoma: Melanocytoma is intensely pigmented, often "velvety," and grows slowly; risk is increased pressure due to pigment dispersion. [37]
• Juvenile xanthogranuloma vs inflammation: in infants - hypema without trauma, yellowish-orange papule on the iris; treated with anti-inflammatory therapy, cautiously with biopsy. [38]

Table 6. Red flags in favor of melanoma

Sign	What to do
Documented growth of the outbreak	Transition from observation to active treatment/resection
Hypema, ectropion of the uvea, feather-like edges	Urgent in-depth verification, consider oncotactics
Engaging the angle over several "hours"	Look for the iridociliary component, plan radiation/combined tactics

Treatment

Observation with photographic documentation is standard for most iris nevi and primary epithelial cysts. Intervals are typically 3-6 months in the first year, then 6-12 months if stable. The criteria for changing tactics are confirmed growth, the appearance of ectropion, feather-like edges, hypema, or angle involvement. The goal is not to "treat everything," but to treat what is changing or threatening function. [39]

Sectoral iridectomy is indicated for localized nodular lesions outside the angle, when both diagnosis and treatment are needed. When the ciliary body is involved, iridocyclectomy is performed. Risks include iris defects, glare, photophobia, and intraocular hemorrhage; these are reduced with careful technique and coagulation of the feeding vessels. The advantage of resection is the possibility of histological examination and a definitive diagnosis.

Plak brachytherapy (iodine-125/palladium-103/ruthenium-106) is an organ-preserving method for nodular or iridocyliary lesions when surgical access is risky or there is angular "seeding." Modern series demonstrate high local controllability and predictable toxicity (cataracts, superficial keratopathy, increased pressure). The choice of isotope depends on the thickness and topography: ruthenium is suitable for thin lesions, while iodine is universal. This method is often preferred for vascular lesions with recurrent hyperema, when coagulation is insufficient. [40]

Proton therapy is used less frequently than for melanoma, but may be considered for diffuse benign, clinically significant lesions with multiple angle-related lesions and a risk of glaucoma, as well as when resection is impossible. Its advantage is precise dose delivery to the anterior chamber while sparing surrounding structures. The decision is made multidisciplinary, taking into account long-term toxicity. Lifelong follow-up is mandatory due to the risk of late complications.

Melanocytoma of the iris is observed more frequently; complications are treated, primarily secondary glaucoma. Hypotensive therapy, including medication, is selected individually; in cases of refractory disease, gentle cyclodestructive procedures (e.g., diode laser) are used, avoiding penetrating surgery in the tumor area. In cases of progression or necrosis with repeated pressure increases, partial resection or local radiation therapy are considered. This is controversial, but justified in experienced centers. [41]

Iris cysts generally do not require intervention. Symptomatic stromal cysts in children can be treated with a combination of puncture and evacuation of the contents, alcohol administration (sclerotherapy), and/or partial resection through a lamellar approach; the choice depends on the size and recurrence. Secondary epithelial cysts after surgery require particular caution: the risk of epithelial "ingroof" dictates a combined approach with cauterizing agents. Any manipulations are performed under conditions that exclude epithelial dissemination. [42]

Vascular anomalies of the iris range from conservative management to minimally invasive procedures. For microhemangiomas with recurrent hyperema, gentle laser photocoagulation is possible, which in some cases has led to stable control without iris defects. If this is ineffective and symptoms are severe, local brachytherapy is acceptable. Intraocular pressure monitoring is essential, and recurrent hemorrhages must be prevented. [43]

Juvenile iris xanthogranuloma is "small" in size, but "high" in glaucoma risk. Treatment is based on anti-inflammatory treatment (topical/systemic steroids) and strict pressure control; iris surgery is avoided due to the risk of bleeding. In case of complications, a pediatric ophthalmologist and (in case of systemic manifestations) a pediatric hematologist are involved. Most cases go into remission, but relapses are possible. [44]

Schwannomas and leiomyomas are rare; if the diagnosis is established and growth is present, "clean" local resection (iridectomy/iridocyclectomy) is preferred, sometimes with intraoperative histology. Neurofibromas in NF-1 are observed or removed for functional/cosmetic indications; a multidisciplinary plan is important due to the risk of multiple lesions. Any doubt regarding the diagnosis of "benignity" is a reason to discuss oncotactics. [45]

Rehabilitation after organ-preserving procedures includes monitoring dryness/keratopathy, correction of iris defects (iris prostheses combined with phacoemulsification), and selection of filtering lenses to combat photophobia and glare. A strict follow-up schedule (see Table 9) is critical for the early detection of late complications and rare recurrences.

Prevention

There is no specific prevention. It is advisable to protect the eyes from intense ultraviolet radiation (glasses with a filter, a visor) and regularly photograph the iris in patients with multiple pigmented lesions to monitor their progress. For neurofibromatosis type 1 and oculodermal melanosis, checkups should be scheduled on an intensified schedule. [46]

Forecast

Overall, the prognosis is favorable: the vast majority of benign lesions remain stable for years and require no treatment. Complications (glaucoma and hyperema) contribute most to quality of life (they need to be recognized and treated proactively). The risk of nevus transformation into melanoma is low, but is higher in patients with ABCDEF features—these patients require more frequent monitoring and a low threshold for active treatment. Long-term intraocular pressure control is important for melanocytomas. [47]

FAQ

Can a nevus of the iris "degenerate"? - Yes, but rarely: in targeted observations, growth into melanoma is about 8% over 15 years. Risk signals: youth, hypema, inferior localization, diffuseness, ectropion, "feathered" edges. [48]
Should cysts always be removed? - No. Most primary cysts are observed; intervention is carried out in case of growth, complaints or risk of complications. [49]
What is "better" for a non-pigmented node: resection or "ray"? - If the diagnosis of benignity is reliable and the node is resectable, local resection is preferable; in case of doubts, angular involvement or recurrence, brachytherapy is discussed.
How often should I come for check-ups? - Usually every 3-6 months during the first year, then 6-12 months if stable; more often if factors ABCDEF are present. [50]
What to do in case of "blood in the eye"? - See an ophthalmologist immediately: it is necessary to exclude a vascular anomaly or juvenile xanthogranuloma and monitor the pressure. [51]

Table 7. Mini-algorithm of actions for a lesion on the iris

Situation	Action
Small stable nevus without red flags	Photo + examination after 3-6 months
Documented Growth/ABCDEF	Advanced imaging (AS-OCT/UBM) + treatment plan
Cyst without symptoms	Observation
Recurrent hypema	Laser/local brachytherapy as indicated
Suspected iridocyliary component	UBM, resection/brachytherapy discussion

Table 8. Common benign iris lesions: what to expect

Diagnosis	Flow	Main risks	Basic tactics
Nevus of the iris	Usually stable	Rare growth → melanoma	Observe; treat for growth/ABCDEF
Melanoma	Slow growth	↑IOP, pigment dispersion	IOP control, in case of progression - resection/radiation
Primary cyst	Stable	Cosmetics, pupillary obstruction	Observation; symptomatic - puncture/resection
Vascular anomaly	Persistent	Hypema	Laser; if it fails, cry
Leiomyoma/schwannoma	Rarely	Melanoma mimics	Local resection in case of growth

Table 9. Recommended monitoring schedule

Period	Frequency	What to control
The first 12 months	Every 3-6 months	Photo, intraocular pressure, goniometry, AS-OCT/UBM as indicated
12-36 months	Every 6 months	Same parameters + early complications
Next	Every 6-12 months	Long-term control, especially with ABCDEF factors