Primitive myxoid mesenchymal tumor of infancy: Case report and review of the literature.

Primitive myxoid mesenchymal tumor of infancy (PMMTI) is an extremely rare soft tissue tumor with only a few cases. Herein, we report a case of 5-months-old girl presenting with a soft tissue mass on the sole of the left foot that recurred 2months after a first resection. The Doppler ultrasound imaging showed abundant blood flow in the tumor. Magnetic resonance imaging (MRI) showed a well demarcated tumor on the sole of the left foot. The surgically resected tumor consisted of primitive mesenchymal tumor cells dispersed in a myxoid background with delicate small blood vessels. Immunohistochemically, tumor cells expressed vimentin but were negative for AE1/AE3, Desmin, Muscle-Specific Actin, MyoD1, Myogenin, CD34, S-100 protein and CD99. Fluorescence in situ hybridization (FISH) showed absence of chromosomal translocation involving SYT and ETV6. Thus, the patient was diagnosed with a primitive myxoid mesenchymal tumor of infancy. To our knowledge, this is the first case of PMMTI affecting the sole of the foot.