Genetic profiling of rhabdomyosarcoma with clinicopathological and radiological correlation

Abstract

Objective: Orbital Rhabdomyosarcoma is a highly malignant tumor predominantly affecting children. Our study adds more understanding of this tumor to ophthalmologists from the clinicopathological, radiological and genetic aspects. Design: A retrospective clinicopathological and radiological study of ocular rhabdomyosarcoma with genetic profiling. Participants: All the cases with confirmed tissue diagnosis of orbital rhabdomyosarcoma presenting at a tertiary eye hospital in Riyadh, Saudi Arabia during the period 1985-2015. Methods: Charts and histological slides of 26 patients were reviewed. DNA was extracted from paraffin-embedded biopsies and genotyping was performed to detect chromosomal abnormalities and Copy-number variations regions. Results: 18 males and 8 females were included with a mean age at presentation of 6.9 years (SD of 4.4). Proptosis and globe displacement were the commonest clinical presentations. Embryonal histopathological type was the commonest (73.1%) with superior orbital involvement (p = 0.024). Using magnetic resonance imaging, the embryonal type showed higher Apparent diffusion coefficient (ADC) value compared to the alveolar type (p = 0.98). Genetic profiling showed Copy-number gain in regions spanning PAX3, DDIT3, Gli, Wnt6 genes. DICER1 gene implication was found in 9 sporadic cases. Conclusion: Rhabdomyosarcoma is rare and occurs with a mean age of 7 years, predominantly among males. The commonest embryonal type is significantly correlated with superior orbital involvement. Radiologically, it shows an ADC of 0.67-0.09 × 10 -3 mm 2 /s. (p = 0.98). The gain in PAX3, DDIT3, Gli1, Wnt6 genes is a new finding while the DICER1 gene implication in the absence of familial hereditary carcinoma is another interesting finding.