Amrami, Kimberly K.

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.

Lipomatosis of nerve (LN), or fibrolipomatous hamartoma, is a rare condition of fibrofatty enlargement of the peripheral nerves. It is associated with bony and soft tissue overgrowth in approximately one-third to two-thirds of cases. It most commonly affects the median nerve at the carpal tunnel or digital nerves in the hands and feet. The authors describe a patient with previously diagnosed hemihypertrophy of the trunk who had a history of large thoracic lipomas resected during infancy, a thoracic hump due to adipose proliferation within the thoracic paraspinal musculature, and scoliotic deformity. She had fatty infiltration in the thoracic spinal nerves on MRI, identical to findings pathognomonic of LN at better-known sites. Enlargement of the transverse processes at those levels and thickened ribs were also found. This case appears to be directly analogous to other instances of LN with overgrowth, except that this case involved axial nerves rather than the typical appendicular nerves.