Indian Journal of Ophthalmology

BRIEF REPORT
Year
: 2000  |  Volume : 48  |  Issue : 2  |  Page : 137--40

Diffuse malignant melanoma of the choroid simulating metastatic tumour in the choroid


J Biswas, R Raghavendra, V Ratra, S Krishnakumar, L Gopal, MP Shanmugam 
 Medical and Vision Research Foundation, Chennai, India

Correspondence Address:
J Biswas
Medical and Vision Research Foundation, Chennai
India




How to cite this article:
Biswas J, Raghavendra R, Ratra V, Krishnakumar S, Gopal L, Shanmugam M P. Diffuse malignant melanoma of the choroid simulating metastatic tumour in the choroid.Indian J Ophthalmol 2000;48:137-40


How to cite this URL:
Biswas J, Raghavendra R, Ratra V, Krishnakumar S, Gopal L, Shanmugam M P. Diffuse malignant melanoma of the choroid simulating metastatic tumour in the choroid. Indian J Ophthalmol [serial online] 2000 [cited 2020 Feb 23 ];48:137-40
Available from: http://www.ijo.in/text.asp?2000/48/2/137/14888


Full Text

We report a case of diffuse choroidal melanoma in a 51-year-old patient presenting as a yellow subretinal mass with secondary retinal detachment. This case highlights the diagnostic difficulty in such cases.

Malignant melanoma of the choroid usually presents as a dome shaped or mushroom shaped pigmented mass with secondary retinal detachment. Such lesions can be easily diagnosed by indirect ophthalmoscopy and ultrasonography. Diffuse malignant melanoma is a rare variant having flat growth pattern with thickness of one-fifth or more than the greatest basal dimension. The incidence of diffuse choroidal melanoma is around 4-5% of all posterior uveal melanomas.[1,2] The tumours typically have a long duration of symptoms, tend to be flat or minimally elevated. They are also frequently misdiagnosed, can often develop secondary glaucoma and even be enucleated for painful blind eye. The risk of metastasis in these patients is higher.[2,3] Among all uveal melanomas diffuse melanomas, have a poor prognosis.[1-4]

 Case report



A 51-year-old male patient presented with complaint of sudden decrease in vision in the right eye of two months duration. He was diagnosed elsewhere to have exudative retinal detachment in the right eye. He experienced flashes of light in the temporal side of the right eye one month prior to examination in our hospital. There was no history of weight loss or previous history of systemic malignancy elsewhere in the body.

His visual acuity was hand movements in the right eye and 6/6 in the left eye. Extraocular movements were full. Slitlamp examination of the right eye revealed a 1+ aqueous flare and cells and 2+ vitreous cells. Left eye was normal. Fundus examination of the right eye showed bullous retinal detachment with a diffuse yellow subretinal mass seen in the macula as well as in the superotemporal quadrant [Figure:1]. Fundus examination of the left eye was normal. A differential diagnosis of choroidal metastasis and malignant melanoma of the choroid with secondary retinal detachment in the right eye was kept. Chest X-ray was normal. Erythrocyte sedimentation rate was l0mmHg in the first hour. Total and differential counts were within normal limits. He had a negative Mantoux reaction. An ultrasonogram showed retinal detachment inferiorly with shifting fluid. A choroidal mass lesion 16.7mm long and 4.3mm thickness was seen on the inferotemporal and superotemporal quadrants extending from the disc. The lesion had an irregular bumpy surface with an initial spike of high reflectivity and internal spikes of moderate to low reflectivity. Choroidal excavation or orbital shadowing was not seen [Figure:2]. Extrascleral or optic nerve involvement was not noticed. Ultrasonogram was serially repeated at one and two months. There was an increase in the maximum height to 4.7 mm. Subsequently magnetic resonance imaging (MRI) of the brain and orbit showed an abnormal, thickened, plaque-like hyperintense mass involving the chorioretinal layers of the right eye with features of retinal detachment [Figure:3].

A differential diagnosis of metastatic carcinoma, inflammatory mass lesion, and diffuse malignant melanoma of the choroid was made. Systemic evaluation at an oncology centre did not reveal any evidence of primary tumour. Computerised tomography scan of the chest and ultrasound of the abdomen were normal. FNAB showed clumps of closely packed cells with hyperchromatic, pleomorphic nuclei, minimal cytoplasm and uveal pigments; necrotic material was also seen adjacent to it [Figure:4]. Initial cytological interpretation was made as metastatic tumour. However, on review of the same slide after enucleation, we felt that our initial interpretation was probably incorrect and the cytological features could be comparable to malignant melanoma of the choroid. The specimen was also subjected to direct smear and culture to rule out tubercular infection. There was no evidence of bacteria, acid-fast bacilli or fungal organisms on direct examination as well as on culture. Polymerase chain reaction for Mycobacterium tuberculosis was negative using IS6110 primer. Repeat evaluation to identify a primary site of malignancy was again negative. The patient was reviewed one month later. Ultrasound showed an increase in size of the tumour, but no extrascleral extension was seen. The patient subsequently lost light perception in this eye. Fundus showed total retinal detachment with increase in the size of the mass. Enucleation was done after discussion with the patient. The globe was fixed in 10% neutral buffered formalin and subjected for histopathological examination.

 Histopathologic Examination



On gross examination of the globe, a brown deeply pigmented tumour mass was seen arising from the choroids 21mm in circumference on both sides of the optic nerve and maximum tumour height was 4mm [Figure:5]. Optic nerve head could not be seen. No extra scleral extension was observed on gross examination. Light microscopic study of the haemotyxlin-eosin stained slide showed that the tumour was composed of mixture of spindle cells and plump epithelioid cells with prominent nucleoli [Figure:6]. Few mitotic figures were seen. Melanin pigments were seen in the cytoplasm of several tumour cells. Multiple vascular channels were seen within the tumour area in the choroid. The retina was detached and there was eosinophilic fluid beneath the retina. Tumour cell infiltration in the anterior portion of the sclera was seen. Optic nerve showed no tumour invasion. Bleaching preparation of the tissue sections also revealed mixture of spindle cells and epithelioid cells with eosinophilic cytoplasm and prominent nucleoli. Separate sections of the vortex veins showed tumour cells in the inferotemporal vortex veins. The superior, inferior and nasal vortex veins showed no invasion by tumour cells.

A pathological diagnosis of diffuse choroidal melanoma of mixed cell type with secondary retinal detachment and invasion into the anterior portion of the sclera and the inferotemporal vortex vein of the right eye was made [Figure:7]. Metastatic evaluation was repeated for the third time. Ultrasonogram of the abdomen and chest X-ray was normal. The patient was advised radiotherapy to the orbit at the local cancer hospital.

The patient was reviewed after two months. No orbital recurrence was noted. Chest X-ray and ultrasound of the abdomen were normal. Liver function tests were also within normal limits.

 Discussion



This case illustrates the diagnostic dilemma in a case of diffuse malignant melanoma of the choroid. With the use of modern diagnostic tests, the incidence of erroneous diagnosis of malignant melanoma of choroid is now quite low.[5] In the Collaborative Ocular Melanoma Study (COMS), out of 1091 eyes of malignant melanoma of the choroid that underwent enucleation, only 6 eyes were histopathologically proven wrong, indicating a misdiagnosis rate of only 0.55%. The six cases, which were clinically misdiagnosed were metastatic carcinoma (4 eyes), haemangioma and melanocytoma (one eye each).[6]

In a recent series by Shields and co-workers[3] out of 3500 consecutive cases of melanoma between 1970 and 1991, 111 cases of diffuse choroidal melanoma of the choroid were diagnosed. The malignant melanomas of the choroid with a basal dimension of 10mm or more showing a flat growth pattern with tumour thickness measuring less than 20% of the tumour diameter were classified as diffuse melanomas of the choroid in their study. Our case had a 21-mm circumference and occupied 40% of the choroid.

Delay in diagnosis is quite common in this variant of malignant melanoma of the choroid. These tumours also have an increased rate of extrascleral extension. Font and co-workers[2] in 1968 found a delay in surgical treatment in 59% of cases in a scries of diffuse malignant melanoma of the choroid and the tumour was not suspected in 40% of the eyes at the time of enucleation in their study. Identification of these variants of malignant melanoma of the choroid is important, as the chance of metastatic potential is around 24% in five years. Shields and co-workers have recently analysed the risk factors for metastasis and found an increase in tumour base and poorly defined margins, correlating with poor prognosis.[3]

As clinical examination and ultrasound did not provide a definite diagnosis in our case, magnetic resonance imaging (MRI) was done. MRI showed hyperintense signal with respect to vitreous on T1 weighted images. T2 weighted image did not show hypointense signal as seen in typical malignant melanoma of the choroid. Gadolinium-DTPA (gadopentetate dimeglumine-diethylenetriamine pentaacetic acid gadolinium) enhanced images increase the sensitivity of diagnosis of melanoma of the choroid as tumour intensity enhancement is usually more marked with choroidal melanoma than uveal metastasis.[9] However, typical enhancement was not seen in our case. This technique can add information to the differentiation of malignant melanoma of choroid from metastatic tumour.

Fine needle aspiration biopsy (FNAB) is a useful investigation in cases of diagnostic dilemma and has been found to be reliable in the diagnosis of uveal melanoma, uveal metastasis, retinoblastoma, lymphoma and leukaemia.[8] In this case as clinical, ultrasound evaluation and a MRI did not provide an unequivocal diagnosis, we did an FNAB under indirect ophthalmoscopic control by the technique described earlier by Shields and coworkers.[7] However, interpretation of FNAB material in suspected malignant melanoma of the choroid is challenging and is not without pitfalls.

Uveal metastatic tumour may have history of detection of malignancy in 75% of the cases at the first presentation to ophthalmologist making the diagnosis easier. But in approximately 25% cases no such history is present at the time of initial diagnosis.[10] An extensive evaluation for primary site may be elusive. Therefore in our case, even in absence of primary malignancy, we could not rule out metastatic tumour of the choroid.

Management of these tumours is usually by enucleation. However, Shields and coworkers have used plaque radiotherapy in 54% of their cases. This is due to the expertise of custom design radioactive plaque at Wills Eye Hospital and the patient preference to preserve the eye.[3] This is possible in the early stage of the disease with nil or minimal secondary retinal detachment. As our patient had large bullous retinal detachment and subsequently lost perception of light we could not consider such therapy.

Our case illustrates a rare presentation of malignant melanoma of the choroid in an Indian patient with nonspecific features on ultrasound and MRI and with inconclusive evidence from fine needle aspiration biopsy highlighting the diagnostic challenge.

References

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