A 2-year-old boy from rural Maharashtra presents with leukocoria (white pupil reflex) in the right eye noted by his mother 3 weeks ago. On examination, the child is otherwise healthy with normal developmental milestones. Intraocular pressure is normal bilaterally. Dilated fundoscopy reveals a white mass arising from the retina in the right eye, with vitreous haze but no obvious extraocular extension. The left eye appears normal on examination. What is the most appropriate next step in management?

Explanation

## Clinical Assessment & Staging Priority **Key Point:** Before any definitive treatment (enucleation, chemotherapy, or radiotherapy) can be planned for retinoblastoma, accurate staging and assessment of tumour extent is mandatory. ### Why Imaging First? The child has a suspected unilateral retinoblastoma with no obvious extraocular signs. However, the management strategy (globe-salvaging chemotherapy vs. enucleation) depends critically on: 1. **Tumour size and intraocular extent** — classified by the International Classification of Retinoblastoma (Groups A–E) 2. **Bilateral involvement** — the left eye must be formally assessed to rule out bilateral disease (present in ~5% of cases) 3. **Extraocular extension** — orbital involvement changes prognosis and treatment urgency 4. **Optic nerve involvement** — assessed on MRI ### Imaging Protocol | Modality | Purpose | | --- | --- | | **Ultrasound B-scan** | Rapid assessment of tumour size, vitreous involvement, calcification (highly specific for RB); done under anaesthesia | | **MRI orbit** | Gold standard for assessing optic nerve involvement, extraocular extension, and bilateral disease; superior soft-tissue contrast | | **CT chest/abdomen** | Staging for metastases (if advanced disease suspected) | **Clinical Pearl:** Calcification on B-scan ultrasound is present in ~80% of retinoblastomas and is highly specific — this finding supports the diagnosis and guides urgency. ### Treatment Algorithm ```mermaid flowchart TD A[Suspected RB on clinical exam]:::outcome --> B[Urgent imaging: US B-scan + MRI]:::action B --> C{International Classification?}:::decision C -->|Group A-C| D[Globe-salvaging chemotherapy]:::action C -->|Group D-E| E{Extraocular extension?}:::decision E -->|No| F[Chemotherapy ± radiotherapy]:::action E -->|Yes| G[Enucleation + systemic chemotherapy]:::urgent B --> H{Bilateral disease?}:::decision H -->|Yes| I[Bilateral treatment planning]:::action H -->|No| J[Unilateral protocol]:::action ``` **High-Yield:** The International Classification (Groups A–E) is the most widely used prognostic system and directly determines whether chemotherapy alone, chemotherapy + radiotherapy, or enucleation is indicated. **Mnemonic: ABCDE Classification** — **A** = small, no risk; **B** = small with risk; **C** = medium; **D** = large; **E** = extensive/phthisical eye. ### Why Other Options Are Incorrect - **Immediate enucleation:** Premature without staging; Group A–C tumours are often salvageable with chemotherapy. - **Chemotherapy without imaging:** Cannot determine if the eye is salvageable or if bilateral disease exists; chemotherapy dosing and route depend on staging. - **Observation:** Retinoblastoma is rapidly progressive and vision-threatening; delays in treatment reduce survival and increase metastatic risk. [cite:Boyd & Melia, Retinoblastoma in Pediatric Oncology textbooks; AIIMS Ophthalmology protocol]