Retinoblastoma associated with orbital pseudocellulitis and high-risk retinoblastoma: a study of 32 eyes

MRI can reliably differentiate optic nerve inflammation from tumor invasion in retinoblastoma with orbital cellulitis

OBJECTIVE

To investigate prevalence and MRI phenotype of retinoblastoma-associated orbital cellulitis. Additionally, this study aimed to identify postlaminar optic nerve enhancement patterns differentiating between inflammation and tumor invasion.

DESIGN

A monocenter cohort study assessed the prevalence of orbital cellulitis features on MRI in retinoblastoma patients. A multicenter case-control study compared MRI features of the retinoblastoma-associated orbital cellulitis cases with retinoblastoma controls.

SUBJECTS

A consecutive retinoblastoma patient cohort of 236 patients (311 eyes) was retrospectively investigated. Subsequently, 30 retinoblastoma cases with orbital cellulitis were compared with 30 matched retinoblastoma controls without cellulitis.

METHODS

In the cohort study, retinoblastoma MRI scans were scored on presence of inflammatory features. In the case-control study MRI scans were scored on intraocular features and postlaminar optic nerve enhancement patterns. Postlaminar enhancement patterns were compared with histopathologic assessment of postlaminar tumor invasion. Interreader agreement was assessed and exact tests with Bonferroni-correction were adopted for statistical comparisons.

MAIN OUTCOME MEASURES

Prevalence of retinoblastoma-associated orbital cellulitis on MRI was calculated. Frequency of intra-ocular MRI features were compared between orbital cellulitis cases and controls. Sensitivity and specificity of postlaminar optic nerve patterns for detection of postlaminar tumor invasion was assessed.

RESULTS

The MRI prevalence of retinoblastoma-associated orbital cellulitis was 6.8% (16/236). Retinoblastoma with orbital cellulitis showed significantly more tumor necrosis, uveal abnormalities (inflammation, hemorrhage and necrosis), lens luxation (all P < 0.001), and a larger eye size (P = 0.012). The inflammatory pattern of optic nerve enhancement (strong enhancement similar to adjacent choroid) was solely found in orbital cellulitis cases, of which none (0/16) showed tumor invasion on histopathology. Of patients with invasive pattern enhancement, 50% (5/10) showed tumor invasion on histopathology. Considering these different enhancement patterns, i.e. suggestive for either inflammation or tumor invasion, increased specificity for detection of postlaminar tumor invasion within the context of orbital cellulitis from 32% (95%CI:16-52%) to 89% (95%CI:72-98%).

CONCLUSIONS

Retinoblastoma cases presenting with orbital cellulitis show MRI findings of a larger eye size, extensive tumor necrosis, uveal abnormalities, and lens luxation. MRI contrast enhancement patterns within the postlaminar optic nerve can differentiate between tumor invasion and inflammatory changes.