Malignant Melanoma of the Iris

Malignant Melanoma of the Iris a 25-Year Analysis of Danish Cases

This study examined malignant melanoma of the iris in Denmark over a 25-year period on the basis of the files of the Eye Pathology Institute. From 1961 to 1985 a total of 80 cases were found (41 males, 39 females; median age 53 years, range 8 - 83). This means an average of 3.2 cases/year with an average population of 4.9 million. In contrast to malignant melanoma of the choroid, an increase was observed. The reason is not known, although exposure to actinic rays may be a factor. More than a third of cases were close to the pupil, a little less than a third invaded the chamber angle/ciliary body. Ten cases were ring melanomas. Half of the tumours were spindle-celled, a quarter mixed and a few epithelioid or naevoid in cell morphology. Iridectomy was performed in 28 cases, primary enucleation in 27 and secondary enucleation in ten. Iridocyclectomy was performed in 15 cases. All patients could be traced. At the date of follow-up (Dec. 1, 1991) eight had died with metastases; four of these were patients with ring melanoma and four with tumours invading the ciliary body. After iridocyclectomy, only one metastatic death was recorded –- a case of incomplete resection. The grave prognosis of a ring melanoma is highlighted.

Iris melanoma

The iris is the least common site of primary uveal melanoma. The prognosis of iris melanoma is better than that of melanoma of the ciliary body and choroid, but the reason for this difference is unclear. One possible explanation is that iris melanoma is smaller than its posterior segment counterparts at the time of diagnosis. Most iris melanomas are spindle cell types, according to a modified Callender classification system. There is evidence that the proliferation of melanocytes of the anterior iris surface (iris plaque) and diffuse stromal invasion may be risk factors for local recurrence and metastasis, respectively.

Iris melanoma: risk factors for metastasis in 169 consecutive patients

OBJECTIVE

To identify risk factors that predict distant metastases of iris malignant melanoma.

DESIGN

Retrospective case series.

PARTICIPANTS

The participants included 169 consecutive patients with microscopically confirmed iris malignant melanoma managed on the Oncology Service at Wills Eye Hospital between 1974 and 1999.

MAIN OUTCOME MEASURES

The main outcome measure was the development of distant tumor metastasis. Cox proportional regression models were used to calculate the risk of eventual metastatic spread.

RESULTS

Of 1054 patients referred with suspicious iris melanocytic tumors (rule out malignant melanoma) over a 25-year period, 169 patients (16%) had microscopically proven iris melanoma, and the remainder (84%) had clinically diagnosed iris nevus. Of the patients with iris melanoma, the mean age at the time of diagnosis was 43 years (median, 45 years; range, 1-90 years). All patients were Caucasian. The mean tumor base was 6 mm (median, 5 mm; range, 1-17 mm), and mean tumor thickness was 2 mm (median, 2 mm; range, 1-4 mm). The mean number of clock hours of tumor involvement in the iris was four, tumor seeding on the iris was four, and tumor seeding into the anterior chamber angle was four. Extraocular extension was present in 10 eyes (6%). The tumor management consisted of local resection (iridectomy, iridocyclectomy, or iridocyclogoniectomy) in 102 patients (60%), enucleation in 51 (30%), plaque radiotherapy in 9 (5%), and observation in 7 patients (4%). Metastasis developed in nine patients (5%). Using Kaplan-Meier life table analysis, metastasis was found in 3% of patients at 5 years, 5% at 10 years, and 10% at 20 years. The clinical factors at initial evaluation predictive of eventual metastasis from iris melanoma included increasing age at diagnosis (P = 0.03), elevated intraocular pressure (P = 0.03), posterior tumor margin at angle or iris root (versus midzone) (P = 0.02), extraocular extension (P: = 0.02), and prior surgical treatment of the tumor elsewhere before referral (versus observation) (P = 0.006). The method of management (resection, radiotherapy, or enucleation) did not have an impact on metastasis.

CONCLUSIONS

Microscopically confirmed iris melanoma demonstrates distant metastasis in 5% of patients at 10 years follow-up. Metastases are more likely to develop in those patients who are older and show tumor features of iris root/angle location with elevated intraocular pressure and extraocular extension.

Treatment of non-resectable malignant iris tumours with custom designed plaque radiotherapy

BACKGROUND

Plaque radiotherapy is the most common method of managing posterior uveal melanoma but its use for iris melanoma and iris metastases has not yet been evaluated.

METHODS

Fourteen patients with non-resectable iris melanoma and four with iris metastasis were treated with plaque radiotherapy. The tumour response to treatment and the local side effects of the radioactive plaque were evaluated.

RESULTS

In the iris melanoma group over a mean follow up of 26 (range 6-75) months, the tumour regressed in 13 of the 14 patients (93%) and recurred as diffuse seeding in one patient (7%). Despite large doses of radiation given transcorneally, the cornea developed epitheliopathy, abrasion, and oedema in only one case each. The major radiation side effects were localised iris vasculopathy without glaucoma in two cases, posterior synechiae in five cases, and cataract in six cases. In the iris metastasis group, tumour regression was observed in all four patients (100%) and radiation side effects were not evident over the relatively short mean follow up period of 8 (range 4-9) months. All of the 14 patients with irradiated iris melanoma have remained systemically healthy without metastasis while three of the four patients with irradiated iris metastases have died of metastases from the primary neoplasm.

CONCLUSION

Custom designed plaque radiotherapy appears to be an effective alternative method of controlling non-resectable diffuse iris melanoma and solitary iris metastasis and has relatively few side effects.

Biomicroscopy and fluorescein angiography of pigmented iris tumors. A retrospective study on 44 cases

The classification of pigmented iris tumors is a difficult clinical problem. Based on the retrospective observation of colour photographs and iris angiograms of 44 pigmented iris tumors observed over 19 years, the authors present an original grading scheme with scores depending on both the biomicroscopical and the fluoroiridographic patterns of the tumors. The biomicroscopical parameters considered were: thickening of the iris in the area of tumor, pupillary distortion and/or ectropion uveae and uneven pigment density. The fluoroiridographic parameters were: early visibility of the anomalous tumoral network, hyperfluorescence inside or around the tumor, and dye leakage at sites remote from the mass. Based on the score of each tumor, the 44 cases were divided into 3 groups with the different degrees of malignancy confirmed by either histological examination or by follow-up behaviour. The authors suggest that routine use of biomicroscopic-fluoroiridographic classification of pigmented iris tumors would be useful.

The long-term outcome of patients undergoing iridocyclectomy

The authors evaluated the long-term results of iridocyclectomy to remove a lesion of the iris or ciliary body in 52 patients. The mean follow-up time was 8.5 years. The excised lesions were benign in 53% of the cases, spindle cell-type melanomas in 19% of the cases, mixed cell- or epithelioid cell-type melanomas in 25%, and an adenocarcinoma of ciliary epithelium in 2%. Visual outcome was generally good, with 43% of the patients achieving visual acuity of 6/7.5 or better and 57% achieving 6/15 or better. In 29% of the patients, enucleation was finally required, and in 10% of the patients there was metastasis of the melanoma. In 11 of the 15 patients who had a subsequent enucleation, the tumor was a melanoma of mixed cell or epithelioid cell type, and in 12 of these 15 patients the surgical margin was involved by the tumor in the iridocyclectomy specimen. All five patients with metastatic disease had melanomas of mixed cell or epithelioid cell type with involvement of the surgical margin in the iridocyclectomy specimen.

Diffuse malignant melanoma of iris with metastases

A 66-year-old man had decreased visual acuity in the left eye. Slit-lamp examination showed hyperpigmentation of the periphery of the iris from 2:30 to 9 o'clock. Gonioscopy disclosed an ill-defined mass involving the angle and extending from 5 to 7:30 o'clock with diffuse pigmentation of the meshwork for 360 degrees. A sector iridectomy was performed inferiorly in his left eye. Histopathologic examination disclosed a diffuse malignant melanoma of the iris, mixed cell type. The patient was free of recurrence when examined at 18, 24 and 30 months following surgery. Two years and ten months following the iridectomy, the patient developed multiple metastatic bony lesions and a mass in the liver. Bone marrow aspiration from the sternum and biopsy from the iliac crest, respectively, showed metastatic malignant melanoma. He died shortly thereafter and an autopsy was not performed. The remote possibility of an occult, intraocular tumor such as a ciliary body melanoma or an internally located melanoma cannot be excluded. Assuming that this is indeed an iris melanoma, as our studies indicate, the rarity of this metastatic iris neoplasm is emphasized by noting that only 37 cases of iris melanomas with presumed metastases have been reported in the literature.

Malignant transformation of an iris melanocytoma. A case report

A 34-year-old Caucasian woman was diagnosed as having a pigmented iris tumor showing recent growth and satellite lesions. The tumor was associated with pigmentation of the anterior chamber angle and secondary unilateral glaucoma. After local excision, histopathologic studies revealed the plump polyhedral cells typical of melanocytoma. However, the examination of additional sections showed evidence of malignancy. The diagnosis of a melanocytoma that transformed into malignant melanoma was made and later confirmed by electron microscopic studies. Following surgical excision of the tumor, the eye maintained normal intraocular pressure. There was no evidence of recurrence 4 years after surgery.

Natural course of melanocytic tumors of the iris

The authors received the charts and photographs of 175 patients who had suspicious melanocytic lesions of the iris and who were followed without treatment. Only eight (4.6%) of these lesions showed clinical evidence of enlargement during follow-up intervals of 1 to 12 years (mean, 4.7 years). Features that were associated with enlargement of the lesion included medial location of the mass on the iris and presence of pigment dispersion onto the adjacent iris and anterior chamber angle structures. Features that were unassociated with growth of the lesion included patient age and sex, intraocular pressure, iris color, tumor size and vascularity, and presence of pupillary distortion, ectropion iridis, and sector cataract. From these results, recommendations are made which can assist the ophthalmologist in the management of pigmented iris lesions.

Iris melanomas

Most iris tumors behave benignly, reflecting their small size and the high proportion of nevi and spindle A melanomas. Of 1,043 reported iris melanomas, 31 metastasized (3%). Metastasis from a spindle A melanoma is not known to occur despite documented growth and local recurrence after excision. If known spindle A melanomas are excluded from all reported spindle cell tumors of the iris, the rate of metastasis for spindle cell tumors is 2.6%. Mixed-cell melanomas have a metastasis rate of 10.5% and epithelioid melanomas a rate of 6.9%. The interval between the histologic diagnosis and death from metastases ranged from three months to 12 years, with an average of 6.5 years. Five- and ten-year mortality rates for different cell types cannot be ascertained. Iris angiography may be useful in defining the limits of tumor involvement but is of uncertain value in differentiating benignancy from malignancy. Of the 31 cases with metastases, 21 included information on the type of surgical procedure used to obtain the histologic diagnosis. In 13 of the 21 cases (62%), the tumors were initially involved with either incomplete excision or inadvertent transection before enucleation.

Iris melanoma. Nevus or malignancy?

Although iris melanomas have an excellent prognosis when diagnosed and treated early, they should not be considered benign lesions. The authors report the orbital recurrence of a melanoma in a patient whose eye had been enucleated 30 years earlier because of an iris melanoma. The clinical, epidemiological and pathological characteristics of iris melanomas are summarized and compared to those of other uveal melanomas. The similarities suggest that iris melanomas are not by nature more benign than other uveal melanomas and that their better prognosis is due to the earlier detection allowed by their more obvious location.

The melanoma controversy. A comparison of choroidal, cutaneous, and iris melanomas

Controversy exists regarding the management of patients with choroidal melanomas. Some experts argue that these neoplasms behave differently than other types of melanomas, and that enucleation rather than tumor burden is responsible for metastases. A review of the literature involving death rates of patients diagnosed with melanomas of the choroid, skin and iris demonstrates the importance of tumor volume as a prognostic indicator. In each instance, the smaller the tumor burden, the better the prognosis. Death rates from metastases involving small choroidal tumors (less than 300 mm) were surprisingly similar to to those from cutaneous melanomas of the same size. Large tumors of the choroid carried a much higher death rate, as did large tumors of the skin. While studies involving iris melanomas reported only a 2.6% death rate, the average volume of an iris melanoma is only 55 mm. We believe that biologically all melanomas have the same potential for metastatic growth and that the size of the tumor may be the most important variable with regard to prognosis.

Metastatic tapioca iris melanoma

A case of metastatic tapioca melanoma of the iris in a 12-year-old girl is reported. The patient had heterochromia, a red painful eye, and was treated for iritis with secondary glaucoma. In the course of 5 months iris lesions with the clinical appearance of tapioca pudding developed, and biopsy disclosed a melanoma. The eye was immediately enucleated, and pathological examination showed a melanoma with predominantly epithelioid-type cells which had infiltrated the angle, the posterior chamber, and the surgical wounds. Conjunctival extension was noted 10 months after enucleation, and regional lymph node metastases were found 4 months later. Previously reported cases are reviewed and compared with the present case.

An en bloc technique for the resection of anterior uveal tumors

We modified trabeculo-iridocyclosclerectomy in a technique for en bloc excision of anterior uveal tumor. A trabeculectomy-type of approach was used, which allowed excision of a rectangular block of sclera, cornea, and trabeculum with attached uveal tissue containing the tumor.