Teaching Case

Case I: A 3-year-old male patient presented with pain in the right eye, insidious in onset with decreasing vision.

Case II: A 2-year-old female patient presented with marked proptosis with eyelid edema of the right eye. She had no vision on the right side. The left eye was normal in appearance with gradually diminishing vision.

Case I: Unilateral Retinoblastoma
A 3-year-old male patient presented with pain and diminishing vision in the right eye. On sonography, a hyperechoic broad based soft tissue mass with coarse calcification was seen in relation to the retina protruding into the vitreous (Fig. 1).On colour Doppler imaging, few vessels were seen in this mass (Fig. 2).High resolution CT showed a well defined soft tissue mass of 7x4 mm in size along the posterior retina with coarse calcification (Fig. 3).

Case II: Bilateral Retinoblastomas
A 2-year-old female patient presented with marked proptosis with no vision in the right eye. High resolution CT showed a large amorphous mass of about 3.6x2.4 cm replacing the right eyeball with a coarse calcified area of 10x6 mm. The extra-ocular musculature was displaced by the mass(Fig. 4, 5). The left eyeball showed mild thickening of the retina with a small speck of calcification.

Retinoblastoma is the commonest primary malignant neoplasm of the retina in childhood. It arises from a cell of neuroepithelial origin and is caused by the inactivation of both copies of a tumour suppressor gene (Rb1) [1]. This hereditary predisposition to retinoblastoma is caused by mutant alleles occurring at the q14 band of chromosome 13 [2].

Retinoblastoma can be multifocal and bilateral (30%) and has an incidence of approximately 1:15 000 to 1:34 000 live births. Retinoblastoma occurs in both familial (40%) and sporadic (60%) patterns. Familial cases typically develop multiple and bilateral tumours. Sporadic cases are always unilateral and unifocal. Trilateral retinoblastoma is rare and usually occurs in the pineal, parasellar, or suprasellar regions [2].

Tumour cells may disseminate through the choroidal vascularisation or may spread beyond the eye through the optic nerve or subarachnoid space. In advanced cases, the tumour may penetrate through the sclera and grow in the orbit. Metastases to the cervical lymph nodes commonly follow extra ocular extension. The most common sites of distant metastases are the CNS, skull, distant bones, and lymph nodes. Spontaneous regression occurs in 1% of cases. Diffuse infiltrating retinoblastoma is a rare histological form of retinoblastoma characterised by diffuse infiltration of the retina without a tumour mass [6]

The diagnosis is usually made before age 2 when a white reflex from the pupil, “cat’s eye” or leukocoria , is diagnosed by opthalmoscopy.

Ultrasound is 80% accurate at diagnosing retinoblastoma. Typically, the tumour mass is hyperechoic with calcification.

High resolution CT is very effective in detecting the calcification in retinoblastomas with high accuracy. CT demonstrates a solid retrolental hyperdense mass with coarse or stippled calcification associated with retinal detachment [3, 4].

MR imaging is a useful diagnostic tool for evaluation of patients with retinoblastoma with high soft-tissue contrast and multiplanar capabilities [5]. MRI shows an iso- to mildly hyperintense mass on T1, hypointense on T2 with moderate to marked enhancement. Associated retinal detachment maybe detected. On postcontrast images extra-ocular extension, optic nerve extension and intracranial spread can be evaluated.

The International Classification of Retinoblastoma is very useful in guiding the treating clinician to choose the most appropriate treatment methods [6].

Retinoblastoma was traditionally treated with enucleation and external beam radiotherapy. However, in the past decade, systemic chemotherapy has become the primary globe-salvaging approach [7].

Early diagnosis by various imaging modalities especially with CT and MRI helps in globe salvaging.