Urachal rhabdomyosarcoma in childhood: a rare entity with a poor outcome.

Background/purpose: Rhabdomyosarcoma (RMS) of the urachus is rare and gathered in the "abdominal and other locations" group for oncological treatment purpose, and therefore not well characterized. Our aim was to assess the clinical and prognostic specific features of urachal primary RMS in childhood.

Methods: We retrospectively reviewed the charts of 8 patients with an urachal RMS treated between 1984 and 2013 in two Pediatric Oncology Departments. Median follow-up was 42 months (18-100).

Results: Urachal RMSs were embryonal in 6, alveolar in 1, and not otherwise specified in 1. Age at diagnosis was 4.4 years (2.6-6). All patients had advanced locoregional extension (IRS IIIIV) and 1 had distant metastasis. All had chemotherapy and surgical resection. Six had external radiotherapy. Four had extensive peritoneal recurrence including 2 with distant metastasis, within a median of 25 months (11-82) after the end of treatment. One had metastatic progression under primary treatment. Four of them died between 18 and 57 months after diagnosis, and 1 is still under treatment for a late recurrence. Only 3 are free of disease after 3.3 to 7.9 years of follow-up.

Conclusions: Pediatric urachal cancer is rare and poorly identified. In our series, RMS was exclusive in this location. Locoregional extension was always advanced. Prognosis was poor despite current multimodal therapy. We underline the need for new therapeutical strategies.