Many types of dorsal neoplasm of early infancy are described in literature ranging from benign to aggressive. Some are more common while others quite unusual. Here, we describe a newborn with a lumbosacral soft tissue mass. Positivity of S-100 and vimentin was compatible with the neural cell line and the high proliferation rate of major activity cells (biopsy Ki67 20%) suggests an aggressive nature. An exclusively surgical approach was chosen and no clinical or radiological signs of recurrence have been observed after 2 years of follow-up. This case is atypical for location, histological pattern, radiological aspect, and clinical behavior. Diagnosis is hard to define and limited to a mesenchymal neoplasia with myxoid tracts. The described aspects raise concerns about clinical and therapeutic approach, classification, and radiological follow-up of sacral tissue masses in newborns.