Small Incision Resection of Iris Melanoma

By Arun D. Singh, MD

Minimally invasive techniques have been adopted in many areas of surgery to reduce patient morbidity, allowing for faster recovery following surgical procedures. An analysis of data from the Nationwide Inpatient Sample (the largest nationwide all-payer database) from 1993 to 2007 demonstrated a major increase in minimally invasive surgery with a corresponding sharp decline in the open counterpart over 14 years.

Iridectomy may be indicated for excision of suspected malignant iris tumors that are circumscribed (less than four clock hours). However, it necessitates a large corneoscleral incision, and failure to adequately close the iris defect can result in a cosmetic defect and photophobia.

We describe a novel surgical technique for internal resection of a circumscribed iris tumor through a small corneal incision combined with gentle sodium hyaluronate (Healon®) aspiration. Small incision removal of a malignant lesion does carry an increased theoretical risk of tumor dissemination and seeding of the anterior chamber if increased tissue manipulation is required. However, this technique may avoid the potential morbidity associated with a large corneoscleral incision, allowing for rapid visual recovery.

CASE STUDY: ASYMPTOMATIC IRIS LESION

A 17-year-old boy presented to the ophthalmic oncology clinic for evaluation of an asymptomatic iris lesion OS. His visual acuity was 20/15 OU. Examination of the left eye revealed a circumscribed 2.1 mm x 1.6 mm pigmented inferior iris lesion with indistinct borders and pigment dusting. Comparison to slit lamp photographs taken five years previously demonstrated growth. The remainder of the ocular examination was within normal limits.

Because of documented growth of the lesion, surgical resection was recommended. A 3.0 mm beveled clear corneal incision was made superiorly at 2 o’clock. A paracentesis incision was made at 10 o’clock. Healon was instilled into the anterior chamber.

Excision with controlled aspiration

Using 25-gauge horizontal vitrectomy scissors and vitrectomy forceps, the lesion was excised en bloc with a visible tumor-free margin. A segment of clear plastic tubing (diameter, 3.5 mm) that had been primed with Healon was inserted into the anterior chamber after the corneal incision was enlarged. Withdrawal of a 3.0 mL syringe attached to the tube allowed gentle and controlled aspiration of the entire iris lesion into the viscoelastic-primed tube. The tube was withdrawn from the anterior chamber, and the lesion was expressed and unfolded onto filter paper and subjected to routine histopathologic processing.

After Healon washout, the iris defect was closed using two interrupted 10-0 prolene sutures placed through paracentesis incisions at 4 and 8 o’clock using a modified Siepser slip-knot technique. The larger corneal incision was closed with three interrupted 10-0 nylon sutures, while the paracentesis was closed with one. On postoperative day 1, visual acuity was 20/15-2, with minimal anterior segment inflammation and without hyphema. The corneal wounds were well-opposed, and intraocular pressure was 20 mmHg.

Histopathology

Histopathologic examination of the resected lesion demonstrated melanoma involving almost the entire specimen. Melanocytic cells (possibly benign nevus cells) were present at the nonpupillary edge of the specimen. The morphology of the malignant population was approximately 95 percent spindle B cells. Mitotic activity was not observed. Immunohistochemistry was positive for Melan-A and negative for smooth muscle actin.

No recurrence to date. The neoplastic growth present in this case, which effaces the architecture of the iris as well as the small epithelioid cells with nucleoli, precludes the diagnosis of a benign nevus, even without finding mitoses. Twelve months postoperatively, visual acuity remains 20/15 and the iris defect is well-opposed, without evidence of recurrence of the tumor.

Modified with permission from: Hood CT, Schoenfield LR, Torres V,
Singh AD. Iris melanoma. Ophthalmology. 2011 Jan;118(1):221-2.

For more information, contact Dr. Arun Singh at ophthalmologyupdate@ccf.org.