Disseminated malignant ectomesenchymoma (MEM): case report and review of the literature.

Malignant ectomesenchymoma (MEM) is a rare soft tissue tumor believed to arise from a pluripotent migratory neural crest cell and composed fo both a mesenchymal element and a neuroectodermal element. The authors report the case of an 11-month-old male who presented with a local abdominal MEM and systemic metastases into lungs, liver, bones, and bone marrow. This is the first reported case of an MEM with initial bone marrow dissemination. The tumor consisted of a neuroblastoma component and a mesenchymal component with sarcomatous features. Diagnosis and therapy were complicated by the histological heterogeneity of the tumor, which also influenced the clinical appearance and course in this case. A literature search revealed 15 other evaluated cases that arose in soft tissue and had adequate clinicopathologic data. Complete surgical resection was the mainstay of treatment, and chemotherapy also appeared to be important. In all reported patients (n = 3) with initial metastases or bone marrow dissemination, as in this case, no cure could be achieved. In patients with disseminated MEM, new therapeutic approaches such as high-dose chemotherapy followed by stem cell rescue should be considered, similar to the current strategy in patients with stage VI neuroblastoma or soft tissue sarcoma.