Assessing the use of FDG-PET in the detection of regional and metastatic nodes in alveolar rhabdomyosarcoma of extremities.

Alveolar rhabdomyosarcoma (ARS) accounts for 20% to 30% of childhood rhabdomyosarcoma and is known to have a worse prognosis than embryonal rhabdomyosarcoma. Metastatic disease is more frequent in patients with alveolar tumors and these children with metastatic disease fare poorly, with a 5-year survival between 20% and 30%. Therefore, ARS represents a significant diagnostic and therapeutic challenge that requires techniques to provide better assessment of the disease than provided by traditional means. F18 fluorodeoxyglucose-positron emission tomography (FDG-PET) depicts the increased metabolism in abnormal tissues, enabling accurate evaluation of suspicious regional and metastatic disease. The new combined PET/CT systems can further improve PET interpretation and affect patient management. The value of FDG in patients with soft tissue sarcomas has been demonstrated in several series, but none specifically in ARS. This report assesses the use of FDG-PET/CT in the detection of regional and metastatic nodes in 3 children diagnosed with ARS of the extremities. All the 3 patients we present had focally increased tracer uptake in nodal stations on a pretherapy PET performed at diagnosis. Tissue confirmation available in 2 patients was negative in 1 patient and positive for metastatic nodal spread in the other. Metastatic axillary disease was possibly also present in the third patient according to his later course of disease.