Radiation induced peripheral nerve tumors: case series and review of the literature.

Purpose: Radiation induced peripheral nerve tumors (PNT) are a rare but known complication of radiotherapy. The clinical and pathologic features of six cases of post-radiation PNT's are reported here, more than doubling the number of known cases reported in the literature.

Methods: We reviewed six cases of radiation induced PNT and performed a review of the current literature on radiation induced neurofibromas.

Results: Patient's ranged in age from 18 months to 49 years at the time of their original diagnosis, with radiation doses to the primary tumor ranging from 24 to 40 Gy with post radiation intervals from 10 to 50 years. The majority of PNT's identified were neurofibromas (3) and schwannomas (3). Nuclear atypia, S100 positive staining and mild-moderate cellularity were common pathologic findings.

Conclusions: There are only a handful of neurofibromas in the 60 cases of PNT's thus far reported. This case series broadens the post-radiation neurofibroma literature. While the pathology of PNT induced transformation is still poorly understood, experiments and pathology are congruent on the possibility of malignant transformation, especially for the "atypical neurofibroma". On the clinical level, this case series lends its support to some, but not all, of the risk factors thought to predispose to the formation of radiation induced neurofibromas. Though rare, the complication of radiation-induced neurofibroma cannot be ignored, especially with the increasing use of focused radiosurgical techniques.