Retinoblastoma is the most common primary intraocular malignant tumor of childhood, originating from retinal photoreceptor precursor cells. It is associated with RB1 tumor suppressor gene mutation and occurs in hereditary (40% — bilateral, multifocal) or sporadic (60% — unilateral) forms. Age at diagnosis is typically under 5 years (average 18 months unilateral, 12 months bilateral). Calcification is present in over 95% of cases and is the most characteristic finding on CT. Trilateral retinoblastoma (bilateral retinoblastoma + pineal region primitive neuroectodermal tumor/pineoblastoma) is an important complication of the hereditary form. Leukocoria (white pupillary reflex) is the most common clinical presentation.
Age Range
0-5
Peak Age
2
Gender
Equal
Prevalence
Rare
Retinoblastoma develops through biallelic inactivation of the RB1 tumor suppressor gene on chromosome 13q14. According to Knudson's two-hit hypothesis, in the hereditary form one mutation is inherited as germline and the second somatic mutation triggers tumor development; in the sporadic form, both mutations occur somatically in the same retinal cell. RB1 protein (pRb) is a critical checkpoint in the G1-S transition of the cell cycle and inhibits the E2F transcription factor; loss of pRb function leads to uncontrolled cell proliferation. Calcification within the tumor develops as dystrophic calcification in necrotic areas and reflects the tumor's high cellular turnover. Spread to vitreous and subretinal space (endophytic and exophytic growth) causes increased intraocular volume and secondary glaucoma or retinal detachment. Optic nerve invasion and choroidal invasion are critical prognostic factors determining the risk of extraocular spread and metastasis.
A calcification-containing intraocular mass on CT in a child under 5 years is practically pathognomonic for retinoblastoma. Calcification is present in over 95% of cases and reflects dystrophic calcification. This finding strongly distinguishes retinoblastoma from other intraocular pathologies in the differential diagnosis (such as Coats disease, persistent hyperplastic primary vitreous, toxocariasis).
Calcification within the intraocular mass on non-contrast CT is the hallmark finding of retinoblastoma, present in over 95% of cases. Calcification may be punctate, coarse, or diffuse in pattern and is generally multifocal. A calcified intraocular mass in a child under 5 years is practically pathognomonic for retinoblastoma. Thin-section (≤1 mm) CT is critical for detecting small calcification foci. Bilateral calcified intraocular masses indicate hereditary retinoblastoma. Globe size should be evaluated; buphthalmos (enlarged eye) indicates secondary glaucoma.
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A soft tissue mass containing calcification within the left/right globe is noted on non-contrast CT, consistent with retinoblastoma as a calcified intraocular mass in childhood.
Retinoblastoma generally shows hyperintense signal relative to vitreous humor on T1-weighted images, reflecting the tumor's high cellularity. The mass appears as a solid structure partially or completely filling the vitreous cavity. Retinal detachment may appear hyperintense on T1 as subretinal effusion (proteinaceous fluid). In exophytic growth pattern, the tumor extends into the subretinal space and pushes the retina anteriorly. In endophytic pattern, the tumor grows toward the vitreous cavity, and vitreous seeding may be seen. Optic nerve invasion is evaluated as nerve thickening and enhancement.
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An intraocular mass with hyperintense signal relative to vitreous is noted on T1-weighted images, consistent with retinoblastoma.
Retinoblastoma generally shows hypointense signal relative to vitreous humor on T2-weighted images, reflecting the tumor's high cellularity. T2 hypointensity is more prominent at calcification foci (susceptibility effect). Retinal detachment and subretinal effusion appear hyperintense on T2 and can be distinguished from tumor. Vitreous seeding may be seen as small T2 hypointense dots. Cystic degeneration or necrosis areas may create focal T2 hyperintense foci within the tumor.
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An intraocular mass hypointense relative to vitreous is noted on T2-weighted images, consistent with a highly cellular tumor and retinoblastoma.
Retinoblastoma shows prominent homogeneous or heterogeneous enhancement on contrast-enhanced fat-suppressed T1-weighted images. Enhancement reflects the tumor's vascularity, and necrotic areas do not enhance. The most critical value of contrast-enhanced MRI is evaluation of optic nerve invasion: enhancement at the optic nerve head or in the prelaminar/postlaminar segment indicates invasion. Choroidal invasion is evaluated as enhancement extending beyond the sclera. Vitreous seeding (endophytic growth) may be seen as small enhancing dots. Contrast-enhanced MRI is also used for pineal region screening in trilateral retinoblastoma assessment.
Report Sentence
A prominently enhancing intraocular mass is noted on contrast-enhanced fat-suppressed T1-weighted images; the optic nerve head should be evaluated for optic nerve invasion.
Calcification within the intraocular mass is seen as hyperechoic foci with acoustic shadowing on B-mode ocular ultrasonography. The mass generally appears with irregular margins, heterogeneous echogenicity, and medium-to-high internal reflectivity. Retinal detachment may be seen as a V-shaped membrane. Vitreous hemorrhage or vitreous seeding creates additional echogenicities in the vitreous cavity. On A-scan, calcification is detected as spikes (high-amplitude reflections). Ultrasonography is used as an initial assessment tool in children and can be performed without sedation; however, MRI is required for extraocular extension and optic nerve evaluation.
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An intraocular mass containing calcification (with acoustic shadowing) is noted on ocular ultrasonography, consistent with retinoblastoma.
Criteria
Carries RB1 germline mutation. Bilateral and/or multifocal involvement. Accounts for 40% of cases. Diagnosed at earlier age (average 12 months). Risk of trilateral retinoblastoma exists.
Distinct Features
Lifetime risk of secondary malignancies (osteosarcoma, soft tissue sarcoma). Pineal region screening (trilateral RB) should be done with MRI. Genetic counseling and family screening are mandatory. Globe-salvage therapy (chemoreduction + local treatments) is preferred.
Criteria
Somatic RB1 mutation. Unilateral, usually unifocal. Accounts for 60% of cases. Diagnosed at later age (average 18 months). Secondary malignancy risk is much lower than hereditary form.
Distinct Features
Globe salvage or enucleation decision is based on tumor size, location, and stage. Genetic counseling is still recommended because 15% may carry de novo germline mutation. Secondary malignancy risk is very low.
Criteria
Bilateral hereditary retinoblastoma + supra/parasellar primitive neuroectodermal tumor (usually pineoblastoma). Develops in 5-15% of hereditary retinoblastoma patients. Usually presents 2-4 years after diagnosis.
Distinct Features
MRI shows an enhancing mass with calcification in the pineal region. Prognosis is poor. Regular MRI screening (every 6-12 months until age 5) is recommended for early detection of trilateral RB in hereditary retinoblastoma patients.
Distinguishing Feature
Rhabdomyosarcoma is an extraocular mass (retinoblastoma is intraocular). Calcification is rare in rhabdomyosarcoma (10%), very common in retinoblastoma (95%+). Rhabdomyosarcoma may cause bone destruction; retinoblastoma is generally confined within the globe.
Distinguishing Feature
Capillary hemangioma is a benign vascular tumor in infants with extraocular location. No calcification. May show flow voids. Retinoblastoma is intraocular and calcified.
Distinguishing Feature
In children, orbital metastasis most commonly originates from neuroblastoma (adrenal) and is an extraocular mass. Bone destruction is common. Urine catecholamines are elevated. Retinoblastoma is distinguished by being intraocular and calcified.
Urgency
emergentManagement
surgicalBiopsy
Not NeededFollow-up
Globe koruma sonrası 3-6 aylık MR takip. Herediter formda 5 yaşına kadar 6 ayda bir beyin MR (trilateral RB taraması). İkincil malignite taraması yaşam boyu.Biopsy is CONTRAINDICATED in retinoblastoma because it increases the risk of tumor dissemination; diagnosis is based on clinical and imaging findings. Treatment approach is determined by tumor stage: globe salvage (chemoreduction + cryotherapy/laser photocoagulation/plaque brachytherapy) or enucleation options are evaluated in intraocular retinoblastoma. Intensive chemotherapy and radiation therapy are required in the presence of extraocular spread or metastasis. MRI is superior to CT for evaluating optic nerve invasion and extraocular extension and is preferred for staging. CT's role is limited to detection of calcification. Genetic evaluation (RB1 mutation analysis) is recommended in all patients.
Globe-sparing treatment (chemotherapy, laser, cryotherapy) is possible with early diagnosis. Enucleation may be required in advanced stages. Genetic counseling is mandatory in hereditary form (bilateral). Screen for trilateral retinoblastoma (bilateral + pinealoblastoma).