Background:

Malignant tumors of peripheral nerve sheath (MPNSTs for its acronym in English) are aggressive sarcomas that occur generally in adulthood and are located mainly on the trunk and lower limbs, with a high association with neurofibromatosis type 1 (NF1).

Case report:

A 34-months-old female infant without NF1 with a palpable abdominal mass is described. The mass corresponded to a retroperitoneal MPNST. The diagnostic approach and management are presented, highlighting the complications and sequelae that occurred during evolution.

Conclusions:

MPNSTs are important despite their low incidence because of their aggressiveness, and should be considered upon the detection of a mass located at paravertebral level or limbs, especially in patients with NF1. The cornerstone of the treatment lies in a complete surgical resection due to the high rate of recurrence, with limited therapeutic response to radiotherapy and chemotherapy. This case presents the clinical manifestations and complications that can be expected with these tumors and their harmful behaviour. The absence of NF1 does not exclude the diagnosis.