Iris Leiomyoma
Updated: Feb 18, 2019
Author: Manolette R Roque, MD, MBA, FPAO; Chief Editor: Hampton Roy, Sr, MD
Overview
Background
Leiomyoma of the iris is a rare, benign intraocular smooth muscle tumor.[1] The tumor often originates from the sphincter or less commonly from the dilator muscles. Studies have found that leiomyomas occur much less frequently than previously reported. Iris leiomyoma has been previously overdiagnosed. Stricter diagnostic criteria involving electron microscopy and immunohistopathology have been added as standards for reporting.
Pathophysiology
The pathogenesis of iris leiomyoma is unclear.[2] Hormones are speculated to play a role in the pathogenesis due to the tumor's similarity to uterine leiomyoma (fibroids) and its predilection to females. Structures in the iris of neuroectodermal origin believed to give rise to the tumor include the sphincter muscle and the dilator muscle. Structures in the iris of mesodermal origin believed to give rise to the tumor include mesenchymal tissue.
Epidemiology
Frequency
United States
The incidence of smooth muscle tumors has been reported as 2.3%, 4%, 9%, and 14.5%, in different published series of iris tumors.
Mortality/Morbidity
No data on mortality and morbidity from iris leiomyoma have been reported. Morbidity may be limited to the occasional presence of secondary glaucoma and decreased vision when the mass reaches the visual axis.
Race
This condition is reported only in white subjects.
Sex
Females are affected more frequently than males.
Age
Cases of leiomyoma of the iris have been seen in patients aged 10-77 years.
Prognosis
The prognosis for vision depends on the location and size of the tumor and is usually excellent.
The prognosis for life is excellent because these tumors are usually benign, slow-growing lesions with no known tendency for metastasis.
Patient Education
At least annual visits with an ophthalmologist are advised for the patient.
Presentation
History
This tumor is usually a benign iris mass that remains clinically stationary for many years. See Physical.
Physical
Lenticular astigmatism may be a subtle sign of an anterior segment tumor, ie, iris leiomyoma.[3]
Leiomyoma of the iris is a localized, flat to slightly elevated mass, often at the region of the sphincter muscle. It is found less commonly in the iris periphery and the anterior chamber angle.
Clinically, the tumor appears nonpigmented (sometimes lightly pigmented), transparent (grayish white to pink colored), and vascular.
Ectropion iridis is a common finding in the area of the tumor.
Leiomyoma of the iris may be difficult to differentiate from an amelanotic iris melanoma.
These tumors can be clinically stationary for many years.
Causes
The cause of leiomyoma of the iris is unknown. See Pathophysiology.
Complications
Continued tumor growth may cause secondary glaucoma.
When the mass reaches the visual axis, a decrease in vision may occur.
DDx
Differential Diagnoses
Workup
Imaging Studies
Anterior segment slit-lamp optical coherence tomography (OCT) is an effective tool in diagnosing as well as monitoring small interval changes in these types of tumors.[3, 4]
Ultrasound biomicroscopy (UBM) may be helpful for evaluating leiomyoma of the iris.[5]
Electron microscopy shows the characteristic features of a smooth muscle neoplasm (thin basement membrane; plasmalemmal vesicles; and numerous, longitudinally aligned cytoplasmic filaments with scattered associated densities).
Hyperfluorescence is noted in the peripheral part of the tumor using fluorescein angiography. Reported as a preoperative mapping procedure in the 1970s, fluorescein angiography is perceived to be of limited value today.
Other Tests
Immunohistochemistry
The findings are consistent with a myogenic tumor.
The tumor cells are positive for smooth muscle actin and desmin.
The tumor cells are negative for S-100 and melanin.
Procedures
Fine-needle aspiration biopsy
This test may be performed when clinical suspicion is high.
The sample may be sent for cytologic study with the use of electron microscopy and immunohistochemistry.
Its value may be limited because of the small sample obtained.
Transillumination
A leiomyoma transmits more light than a melanoma.
The more peripheral part of the tumor may be translucent.
Even amelanotic melanomas contain small amounts of melanin sufficient to cast a relative shadow.
Histologic Findings
Light microscopy shows the characteristic appearance of a leiomyoma with interlacing, densely packed, elongated, spindle-shaped cells, with long oval nuclei that tend to be arranged in a palisading manner, and granular eosinophilic cytoplasm of the cells and myofibrils.
This is best seen with phosphotungstic acid hematoxylin stain.
Examples of histologic findings are shown in the images below.
Leiomyoma of iris. (A) Spindle cell tumor arising in region of sphincter muscle of iris. Hematoxylin and eosin, X30. (B and C) Tumor is composed of uniform spindle-shaped cells with an abundant admixture of fibrillary cell processes. Hematoxylin and eosin, X500. Armed Forces Institute of Pathology Acc. 68490.
(A) Incidental iris leiomyoma (arrow) in 16-year-old female with uveitic glaucoma removed at time of glaucoma procedure. Courtesy of Alan L. Robin, MD. (B) Tumor (between arrows) is composed of spindle-shaped cells with an abundant admixture of fibrillar material. Hematoxylin and eosin, X340. (C) The cells stain positively for smooth muscle actin. Immunoperoxidase, X340. EP 96159.
Treatment
Medical Care
Regular photographic documentation of the iris mass is necessary in patients with leiomyoma of the iris.
Surgical Care
Conservatism is suggested in the management of demarcated iris tumors, particularly for those tumors in the central part of the iris.
When the visual field is threatened, complete excision of the tumor in the pupillary zone is safe.
Phacoemulsification of sectoral cataracts may be performed. Toric intraocular lens implants may address the corneal astigmatism.[3]
Pupillary repair and reconstruction may be warranted on some occasions.
In primary ciliary body leiomyoma extending into the iris and the anterior chamber (see images below), sclerouvectomy has been found to be beneficial.[6]
Ciliary body leiomyoma extending anteriorly.
Ciliary body leiomyoma extending anteriorly.
Ciliary body leiomyoma extending anteriorly.
Ciliary body leiomyoma extending anteriorly.
Consultations
Ocular pathologist
Having the opinion of a subspecialist may prove worthwhile. Appropriate photographic documentation is necessary.
The specimen obtained during biopsy should be appropriately submitted to an ocular pathologist for proper immunohistochemistry and ultrastructural study.
Long-Term Monitoring
Once a diagnosis of leiomyoma is confirmed by ultrastructural analysis after excisional biopsy, no further treatment of this benign lesion is necessary.
If the excisional biopsy is large, diplopia and glare may potentially become complaints. Addressing these issues appropriately is necessary.
Further Inpatient Care
In some centers, admission may be necessary after performing an excisional biopsy.
Monitoring for infection, wound leakage, anterior chamber depth, and pupillary status is required.
Inpatient & Outpatient Medications
Aside from the use of an eye shield, oral painkillers, and topical antibiotics and steroids after the procedure, no further special care is necessary.
Appropriate topical ophthalmic medications may be provided in the advent of an excisional biopsy.