A rare case of adult onset retinoblastoma.

Retinoblastoma usually manifests before five years of age. Retinoblastoma in an adult is extremely rare. Twenty-three cases of retinoblastoma in adults 20 years or older have been reported in world literature. We report a case of adult onset retinoblastoma in a 29-year-old female. Our patient had unilateral endophytic retinoblastoma with vitreous seeds and calcification on ultrasonography. She underwent enucleation with silicone ball implantation and the diagnosis was confirmed histopathologically. The diagnosis of retinoblastoma should be kept in mind in cases presenting with a white mass lesion of unknown etiology, in the fundus of an adult.

Introduction

Retinoblastoma is the most common primary intraocular malignancy in children with a reported incidence ranging from one in 15,000 to one in 18,000 live births.[1] More than 90% of the cases present before five years of age.[2] Adult-onset retinoblastoma is an extremely rare entity and for this reason it is usually not considered in the differential diagnosis of a retinal or intraocular mass in an adult.[2-5] In 1919, Maghy reported a well-documented retinoblastoma in a 20-year-old female. Since that report, an additional twenty-two cases of retinoblastoma have appeared in world literature in patients 20 years or older [Table 1]. We report a rare case of unilateral retinoblastoma, with histopathological confirmation, in a 29-year-old woman.

Table 1

Summary of reported cases of retinoblastoma in adults

Case Report

A 29-year-old female presented to us with a history of sudden painless diminution of vision in the right eye, of three days′ duration. On examination, visual acuity was 20 / 40 in the right eye and 20 / 20 in the left eye. The left eye was normal. The right eye revealed retrolental cells on slit lamp examination. The anterior segment examination did not exhibit any other abnormalities. Intraocular pressure was normal. Fundus examination showed a large, whitish, elevated mass lesion inferotemporal to the disc [Figure 1]. The ultrasonographic study revealed a solid mass lesion measuring 11.53 × 4.16 × 4.74 mm, of moderate-to-high internal reflectivity, with calcification [Figure 2]. Computed tomography of the orbit and brain showed an endophytic soft tissue mass emanating from the retina, with foci of calcification, and there was no optic nerve or extraocular involvement. Systemic examination was carried out to rule out diseases such as tuberous sclerosis.

Figure 1

Fundus photograph showing a whitish, nodular, endophytic mass lesion with multiple vitreous seedings

Figure 2

B-scan ultrasonography showing mass lesion with moderate-to-high internal reflectivity with calcification

The differential diagnosis included adult-onset retinoblastoma, metastatic carcinoma, astrocytoma, and amelanotic melanoma. Enucleation and silicone ball implantation were performed. Gross examination of the cut section of the globe revealed a white tumor mass arising from the retina, measuring 4 mm at its base and 6 mm in height. A histopathological examination confirmed the diagnosis of retinoblastoma, which was endophytic, well-differentiated, with Homer-Wright rosettes, and no choroidal or optic nerve invasion [Figure 3]. Eight months later, the patient presented with exposure of the silicone ball implant, and subsequently she underwent removal of the exposed silicone ball implant, and implantation of the hydroxyapatite sphere with a scleral graft. After a span of two years, she developed pyogenic granuloma and underwent an excisional biopsy. There was no recurrence of tumour in her orbit on the last follow-up examination, four years following enucleation.

Figure 3

Photomicrograph showing multiple Homer-Wright rosettes (H and E, ×200)

Discussion

Retinoblastoma is a malignant neoplasm originating from photoreceptor precursor cells. Retinocytoma is a rare benign retinal tumor linked to RB1 gene mutation. It is not known whether retinoblastoma in an adult occurs de novo or is preceded by a retinocytoma.[4] There is a possibility of the presence of retinocytoma, which undergoes oncogenic mutations, resulting in the malignant transformation of the retinocytoma. Singh et al. stated that the risk of malignant transformation of a retinocytoma into a retinoblastoma is 4%.[6] Patients with retinocytoma must be kept in follow-up for several years due to the possibility of malignant transformation. All reported cases of adult-onset retinoblastoma in the literature are sporadic and unilateral.

The differential diagnoses of a white mass lesion in the ocular fundus of an adult include, metastatic carcinoma, amelanotic melanoma, lymphoma, astrocytoma, retinoblastoma, retinocytoma, endophthalmitis, panophthalmitis, and inflammatory diseases of the retina. Retinoblastoma in an adult creates a diagnostic dilemma owing to its low frequency.[7] The presence of Inflammation, vitreous hemorrhage, and cataract further augment difficulties in diagnosis.[4] Ultrasonography and a computed tomography scan may or may not reveal calcification, which is characteristic of retinoblastoma in children. Calcification is not an important finding in adult-onset retinoblastoma.[7] In our patient, calcification was present. Cases with diagnostic dilemma might undergo fine-needle aspiration cytology and immunohistochemistry with neuron-specific enolase.[8]

Histopathology of the enucleated specimen confirms the diagnosis and identifies the level of differentiation. Tumors with foci of Flexner-Wintersteiner rosettes are classified as differentiated retinoblastomas, whereas, tumors devoid of Flexner-Wintersteiner rosettes and fleurettes are classified as undifferentiated retinoblastomas. Our patient had an endophytic, well-differentiated retinoblastoma with foci of Homer-Wright rosettes.

Enucleation was the primary modality of treatment in a majority of reported cases, as the tumor was detected at an advanced stage. Our patient also underwent enucleation with silicone ball implantation, which was replaced by a hydroxyapatite implant.

This report highlights the fact that the presence of an amelanotic mass lesion in the fundus of an adult should raise the suspicion of a retinoblastoma. Due to the aggressive nature of the tumor and the metastatic potential, prompt diagnosis and management is essential.