Rhabdomyosarcoma With Diffuse Bone Marrow Metastases

Rhabdomyosarcoma is a highly aggressive cancer that is generally considered a disease of childhood. A vast majority of cases occur in those below the age of 20. Rhabdomyosarcoma can occur in any soft tissue in the body but is primarily found in the head, neck, orbit, genitourinary tract, genitals, and extremities. Prognosis is closely tied to the location of the primary tumor and the extent of metastatic spread. As with most sarcomas, rhabdomyosarcoma has a pattern of hematogenous spread which favors metastasis to the lungs. Other common areas include bone marrows, liver, breasts, and brain. One unusual pattern is the presence of diffuse bone marrow metastases in absence of significant soft tissue disease other than primary (no distant nodal disease, absence of visceral disease in chest and abdomen). Frequently in such cases, patients may have initial presentation similar to hematologic malignancy especially when the primary tumor is not evident. This pattern has been rarely described in the radiology literature. This pattern appears to be well documented in pathology literature. Even more rarely, in some cases, the primary tumor site may not be found after imaging and may remain undetermined even postmortem - only diagnosed by bone marrow aspiration. Awareness of this unique pattern is clearly important for radiologists, especially pediatric radiologists, as misdiagnosis can lead to delay in appropriate treatment that ultimately results in increased mortality. We present a case of rhabdomyosarcoma with this unique pattern of bone marrow metastases in which initial differential diagnosis favored a leukemic picture. This paper will go over the diagnostic techniques utilized throughout our patient’s disease course as well as treatment.