Embryonal rhabdomyosarcoma with a der(16)t(1;16) translocation

Area of Science:

• Pediatric Oncology
• Cytogenetics
• Molecular Biology

Background:

• Embryonal rhabdomyosarcoma (ERMS) is a common pediatric cancer, primarily affecting the genitourinary tract and head/neck regions in young children.
• ERMS typically presents with hyperdiploidy, but lacks consistent structural chromosomal alterations, unlike alveolar rhabdomyosarcoma (ARMS).
• ARMS is characterized by specific gene fusions, such as PAX3-FOXO1A or PAX7-FOXO1A, resulting from t(2;13) or t(1;13) translocations.

Observation:

• A case of ERMS in a 22-month-old male presented with a hyperdiploid karyotype and a secondary, nonrandom chromosomal aberration: der(16)t(1;16)(q22;q24).
• This specific translocation resulted in an unbalanced rearrangement involving 1q and 16q chromosomal material.
• Fluorescence in situ hybridization and reverse transcriptase-polymerase chain reaction analyses confirmed the absence of FOXO1A, PAX3, or PAX7 gene rearrangements and fusion transcripts.

Findings:

• The study identified an unbalanced t(1;16) translocation in an ERMS tumor.
• This translocation was observed in a hyperdiploid genetic background, with additional copies of chromosomes 2, 7, 8, 10, 12, 13, 19, and 20.
• Crucially, the ERMS tumor lacked the characteristic PAX gene fusions associated with ARMS.

Implications:

• The findings suggest that the t(1;16) translocation may represent a secondary genetic event in ERMS.
• This observation expands the known cytogenetic landscape of rhabdomyosarcoma subtypes.
• It highlights the importance of comprehensive cytogenetic analysis in identifying novel genetic alterations in pediatric cancers, even in the absence of typical fusion genes.