When should one suspect malignant transformation of a neurofibroma into an MPNST?
Pain and rapid growth are the two main findings that raise suspicion for malignant transformation of a neurofibroma into an MPNST. Whereas malignant transformation of a neurofibroma into MPNST rarely occurs in sporadic cases, 2% to 5% of patients with NF-1 may develop an MPNST. MPNST arising in patients with NF-1 tends to have higher grade, larger size, and more aggressive behavior compared to that arising sporadically. A solitary, large, heterogeneous, enhancing retroperitoneal mass is typically seen with MPNST, although no specific CT or MR imaging features are available that can reliably differentiate MPNST from benign neurogenic tumors.
