Optic nerve invasion of non-juxtapapillary uveal melanoma: a rare occurrence

Abstract

A 44-year-old man presented with complaints of pain and discomfort in his left eye (OS). On examination, he had bare perception of light in OS and had a diffuse pigmented mass lesion in the nasal quadrant of the bulbar conjunctiva, associated with neovascularisation of the iris and iridocyclitis, with no fundus view. Intraocular pressure OS was 40 mm Hg. B-scan ultrasonography OS revealed an intraocular mass with thickened sclerochoroidal complex. A clinical diagnosis of OS ciliochoroidal melanoma with extraocular extension was made. He underwent OS extended enucleation with implant. Histopathological examination confirmed the diagnosis of ciliochoroidal melanoma with tumour extension into the optic nerve posteriorly and the extrascleral tissues anteriorly. There was no evidence of systemic metastasis. Even in a case of non-juxtapapillary uveal melanoma, poor vision and high intraocular pressure are clinical indicators of optic nerve tumour invasion.

Background

A relatively rare disease, uveal melanoma is the most common primary intraocular malignancy in adults, primarily found in Caucasian populations, with a mean age-adjusted incidence of 5.1 cases per million per year.¹ The most common site for uveal melanoma is the choroid. In a review of 8033 patients by Shields et al,² choroid was found to be the origin in 7256 cases (90%), ciliary body in 492 (6%) and iris in 285 (4%) patients. Systemic metastasis usually occurs in the liver.^{3 4} Extraocular tumour extension occurs through the sclera along the ciliary vessels and nerves. Optic nerve invasion of the uveal melanoma is rare and has been reported in 0.6%–7% of cases, and is usually associated with juxtapapillary tumours.^5–14 We report a case of non-juxtapapillary ciliochoroidal melanoma with optic nerve invasion.

Case presentation

A 44-year-old man presented with complaints of pain and discomfort in his left eye (OS) in the last 1 week associated with a mass lesion for 8 months. Eye vision was perception of light with inaccurate projection of rays in all four quadrants. Intraocular pressure OS was 40 mm Hg by Goldmann applanation tonometry. On examination, there was diffuse conjunctival congestion with 15×10×7 mm pigmented elevated mass lesion in the nasal quadrant of the bulbar conjunctiva, 2 mm away from the limbus, extending from 8 to 10 o’clock hours (figure 1A). Anterior chamber examination revealed flare and cells of 2+, with ectropion uvea and 360° neovascularisation of the iris. There was anterior subluxation of the cataractous lens, causing shallowing of the anterior chamber (figure 1B). There was no fundus view due to cataractous lens. No regional lymphadenopathy was found on palpation of the preauricular, submandibular and anterior cervical lymph nodes.

Figure 1.

Clinical presentation of uveal melanoma (A). Clinical photograph showing pigmented mass lesion in the left eye of the patient. (B) High magnification clinical photograph showing the pigmented lesion along with shallow anterior chamber and cataractous lens. (C) Ultrasound B-scan showing hyperechoic vitreous cavity with dome-shaped intraocular lesion. (D) Ultrabiomicroscopy showing thickened sclerochoroidal complex with a membrane in the anterior chamber.

Investigations

B-scan ultrasonography revealed a hyperechoic vitreous cavity with dome-shaped mass almost filling the entire vitreous cavity (figure 1C). Ultrasound biomicroscopy revealed a thickened sclerochoroidal complex with inflammatory membrane in the anterior chamber (figure 1D).

Differential diagnosis

A clinical diagnosis of OS ciliochoroidal melanoma with extraocular extension was made. No other differential diagnosis was considered.

Treatment

With a diagnosis of OS ciliochoroidal melanoma with extraocular extension, the patient underwent OS extended enucleation with implant, including removal of the extrascleral tumour with overlying conjunctiva along with the globe. The surgery was performed by ‘no-touch technique’, ensuring that the tumour was not touched any time during the surgery so as to avoid tumour seeding,

Outcome and follow-up

Histopathological examination showed tumour cells with spindle to polygonal morphology involving the ciliary body and choroid (figure 2A), invading the trabecular meshwork, sclera and the extrascleral soft tissue anteriorly (figure 2B), and invading the vitreous, retina (figure 2C), lamina cribrosa and 0.5 mm postlaminar optic nerve posteriorly (figure 2D). Of the tumour cells 90% showed necrosis, with 10% viable cells, which were of spindle cell morphology. Resected margins of the conjunctiva were free of tumour.

Figure 2.

Histopathology of uveal melanoma. (A) Whole mount of the enucleated eyeball showing ciliary body pigmented tumour with tumour cells in the vitreous and retina surface. H&E stain, 0.5× magnification. (B) Photomicrograph showing ciliary body tumour with invasion of tumour cells in the trabecular meshwork, sclera and extrascleral soft tissue. H&E stain, 1× magnification. (C) Photomicrograph showing necrosed tumour cells with pigment granules in vitreous. H&E stain, 10× magnification. (D) Photomicrograph showing optic disc cupping with tumour invasion of lamina cribrosa and postlamina cribrosa. H&E stain, 5× magnification.

The patient was doing well postoperatively. He subsequently underwent external beam radiotherapy to the left orbit. A customised ocular prosthesis was dispensed for cosmetic rehabilitation. A whole-body positron emission tomography scan was done to rule out systemic metastasis, which showed no hypermetabolic lesions elsewhere in the body.

Discussion

Uveal melanoma is the most common primary intraocular malignant tumour in adults, comprising 3%–5% of all melanomas.^{15 16} Optic nerve invasion rarely occurs and is seen in 0.6%–7% of cases.^5–14 In a review of 157 patients with uveal melanoma with optic nerve invasion, it was noted that prelaminar or laminar invasion occurs in 54% of cases and postlaminar invasion in 46% of cases.¹¹ The factors predictive of postlaminar optic nerve invasion by univariate analysis included older age (>70 years), poor vision of light perception or worse, nil view of the fundus, tumour >15 mm, juxtapapillary tumour location and raised intraocular pressure.¹¹ Our patient had all these predictive features of postlaminar optic nerve invasion, except that he was a young patient at age 44 and the tumour was not juxtapapillary in location. Poor vision and raised intraocular pressure are more important factors in predicting optic nerve invasion.6 11 14 17–20 Our patient had both these features. Of cases with optic nerve invasion, juxtapapillary location is noted in 69% of cases, while 31% of cases are away from the optic disc.¹¹ In our case, the ciliary body was the tumour epicentre.

The mechanism of optic nerve invasion includes direct peripapillary invasion with tumour extension between the end of the Bruch’s membrane and the border tissue of Elschnig, or direct extension through the border tissue of Elschnig (57%), retinal invasion with rupture of the Bruch’s membrane or spread of the tumour on the inner retinal surface (23%), transvitreal invasion with dispersion of the tumour cells into the vitreous or extravasation of the tumour cells through adjacent retinal vessels, or migration of the tumour cells with vitreous haemorrhage (10%), or a combined mechanism (10%).^{11 21} In our case, the probable mechanism of tumour invasion is a combined mechanism with transvitreal invasion via dispersion of tumour cells in the vitreous, retinal invasion with rupture of the Bruch’s membrane and spread along the inner retinal surface.

The risk of metastasis is marginally higher in patients with postlaminar optic nerve invasion (63%) compared with those with prelaminar or laminar optic nerve invasion (53%) or those without optic nerve invasion (61%).¹¹ Similarly, the melanoma-related mortality is higher in patients with postlaminar optic nerve invasion. Although liver is the most common site of metastasis in these patients with optic nerve invasion, central nervous system metastasis can also occur in patients with optic nerve invasion.¹¹ Although our patient was free of metastasis at 1-year follow-up, a long-term follow-up is warranted.

Learning points.

• Optic nerve invasion in a case of uveal melanoma is extremely rare.

• Although juxtapapillary tumour location is a risk factor for optic nerve invasion, it can occur even in tumours away from the optic nerve.

• Even in a case of non-juxtapapillary uveal melanoma, optic nerve invasion should be suspected if the patient presents with poor vision and raised intraocular pressure.