Persistent mass after treatment for orbital rhabdomyosarcoma.

purposeTo report a case of orbital rhabdomyosarcoma and highlight the treatment approach to the dilemma of a residual mass. OBSERVATIONS: An eleven-year-old boy was diagnosed with Stage 1, Group III embryonal rhabdomyosarcoma in the orbit. After completing a 24-week treatment regimen of chemotherapy and radiation, imaging showed a large persistent mass with erosion through the medial wall. It was uncertain whether the erosion was due to radiation osteonecrosis or to advancing tumor, creating a treatment dilemma for the providers. A repeat biopsy was planned. During the procedure, the mass was completely excised due to ease of removal, and the biopsy showed completely treated tumor. MRI surveillance at four years follow up showed that the patient remains tumor-free. CONCLUSIONS AND IMPORTANCE: Rhabdomyosarcoma was once a disease with a very poor outcome, but advances in imaging, chemotherapy, and radiation therapy have improved the prognosis of these patients. What was once a surgical disease treated with morbid resection is now predominantly a medical disease diagnosed with biopsy and treated with chemotherapy and radiation. However, such patients may have a residual mass after completing treatment. This situation presents a challenge, as it may not be clear whether the persistent mass is active tumor or treated tumor. This report describes the presentation and management of such a case in the orbit and demonstrates that a residual orbital mass may remain and represent completely treated tumor.