American Society for Peripheral Nerve

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Perineural tumor spread in pelvic malignancies
Stepan Capek, MD; Benjamin M. Howe, MD; Kimberly K. Amrami, MD; Robert J. Spinner, MD
Neurosurgery, Mayo Clinic, Rochester, MN

Introduction: Perineural tumor spread in pelvic malignancies has emerged as an anatomic explanation for selected cases of neoplastic lumbosacral plexopathy. We present a case series and provide summarized clinical and imaging characteristics. To our knowledge a similar series has not been presented yet.

Material and methods: We retrospectively reviewed cases concluded as perineural tumor spread and excluded cases without histological confirmation of the perineural spread and cases with widespread pelvic disease infiltrating the plexus. We reviewed clinical data and imaging studies, and recorded all time-points.

Results: Ten patients (8 men, 2 women) were included in the study (prostate cancer n=5; rectal cancer n=2, bladder cancer n=2, cervical cancer n=1). Mean age was 69 years (range 48-85 years). Pain was the initial symptom in 6 patients, pain and weakness in 1 patient, weakness in 1 patient, and 2 patients were asymptomatic. In 1 patient the diagnosis of lumbosacral plexopathy preceded the tumor by 3 months, in other patients the mean time from the tumor diagnosis to the initial symptom was 67 months. On presentation, 6 symptomatic patients had pain, sensory loss and weakness corresponding to the affected nerves. On MRI (n=10) the affected nerves were enlarged and demonstrated thick perifascicular enhancement. MRI finding correlated with increased uptake on FDG PET/CT (n=4) and 11C-Choline PET/CT (n=3) scans. EMG (n=9) demonstrated lumbosacral plexopathy in 8 patients; in 1 patient it was normal. Six patients had no signs of distant metastatic disease at the time of the lumbosacral plexopathy diagnosis; two patients had metastases in lungs, one patient had metastases in pelvis and one had solitary metastasis in liver. Seven patients were alive at the time of the last follow-up. Mean time from the initial symptom to the last follow-up was 51 months.

Discussion: Our proposed route of the tumor spread is from the pelvic organ to the lumbosacral plexus and beyond using the splanchnic nerves as a conduit. We believe this theory can explain selected cases of neoplastic lumbosacral plexopathy. The route of spread can be visualized as a unilaterally thickened and enhancing perirectal fascia containing the pelvic and sacral splanchnic nerves.

Conclusion: We presented a series of 10 cases of perineural tumor spread in pelvic malignancies. We believe that this mechanism is an otherwise underrecognized cause of morbidity and recurrence in pelvic cancer patients.

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