Howe, Benjamin M.

Perineural tumor spread in prostate cancer is emerging as a mechanism to explain select cases of neurological dysfunction and as a cause of morbidity and tumor recurrence. Perineural spread has been shown to extend from the prostate bed to the lumbosacral plexus and then distally to the sciatic nerve or proximally to the sacral and lumbar nerves and even intradurally. The authors present a case of a bilateral neoplastic lumbosacral plexopathy that can be explained anatomically as an extension of the same process: from one lumbosacral plexus to the contralateral one utilizing the dural sac as a bridge between the opposite sacral nerve roots. Their theory is supported by sequential progression of symptoms and findings on clinical examinations as well as high-resolution imaging (MRI and PET/CT scans). The neoplastic nature of the process was confirmed by a sciatic nerve fascicular biopsy. The authors believe that transmedian dural spread allows continuity of a neoplastic process from one side of the body to the other.

Several groups have reported cases of rectal cancer with carcinomatous involvement of the lumbosacral plexus and sciatic, obturator, pudendal, or spinal nerves. To our best knowledge, clear examples of perineural tumor spread in rectal carcinoma have not yet been described. We retrospectively reviewed clinical data and imaging studies of three patients with primary or recurrent rectal cancer involving the lumbosacral plexus. Imaging studies included MRI and 18FDG PET/CT scans in all (n = 3) patients, histological samples were available in two (n = 2). Imaging studies demonstrated distinct features of tumor spread from the organ to the plexus and beyond in all cases (n = 3), histological specimens demonstrated perineural involvement thus supporting our theory (n = 2). We present these three cases of perineural tumor spread in rectal cancer as a proof of concept. We hypothesize that not only our cases, but other similar reported cases can be explained anatomically by extension of the rectal cancer to the inferior hypogastric plexus with perineural tumor spread to the lumbosacral plexus using the pelvic and sacral splanchnic nerves as conduits. Once the tumor reaches the lumbosacral plexus, it can continue to spread proximally or distally. We believe that perineural spread of colon cancer represents an important, under‐recognized mechanism of recurrence to neighboring major nerves in the pelvis. Clin. Anat. 28:136–143, 2015. © 2014 Wiley Periodicals, Inc.