LAUSR

Direct involvement of the femoral nerve in colorectal cancer is rare. We present a case of a completely excised recurrent mucinous adenocarcinoma, which invaded the right psoas muscle and encased the right femoral nerve, with full preservation of patient’s neurological function. A 64-year-old obese woman presented in March 2015 with radiological evidence of peritoneal recurrence in the right pelvic sidewall and spleen. The patient had previously undergone an ileocolic resection (2012) with subsequent excision of a right iliac fossa mass, omentectomy and heated intraperitoneal chemotherapy (HIPEC) with mitomycin C in 2013. Original histology demonstrated a moderately differentiated mucinous adenocarcinoma, originating in the base of caecum, with disseminated mucinous deposits. The patient had remained asymptomatic following the previous surgery and recurrence was noted on routine positron emission tomography (PET)/computed tomography (CT) surveillance scanning. The CEA level remained normal. Preoperative PET/CT revealed a 48 × 61 mm mass indistinguishable from the iliopsoas muscle and low-density nodules associated with the splenic capsule; however, no evidence of extra-abdominal disease. After reviewing the case at a multidisciplinary meeting and following a detailed discussion with the patient and her family, we proceeded to a laparotomy with curative intent (given the potential resectability and absence of extra-abdominal disease). At operation, a mass was seen in the right iliac fossa adherent to the right iliacus muscle (Fig. 1). The tumour encased the right femoral nerve, as the nerve descended between the psoas major and the iliacus muscles (Fig. 2). Careful sharp dissection was undertaken with complete macroscopic removal of the tumour, leaving the femoral nerve intact (Figs 2,3). The femoral nerve course in the right iliac fossa is clearly visible in Figure 3. Following removal of the mass, surgery was completed with a splenectomy, removal of all peritoneal mucinous deposits and HIPEC using oxaliplatin and concurrent intravenous 5-fluouracil. Post-operative recovery was uneventful and the patient was discharged on day 15. Preand post-operative CEA remained low. Lower limb mobility was intact on discharge, but the patient complained of numbness in the anteromedial thigh (consistent with distribution of the anterior cutaneous branch of the femoral nerve). On further follow-up with allied health, at 6 weeks, the patient is fully independent at home, with no motor or sensory deficits. The patient has no neuropathic pain. Histological analysis confirmed a recurrent mucinous moderately differentiated adenocarcinoma in the right iliac fossa and on the spleen, with widespread peritoneal mucinosis. Resection margins were clear. Surgical treatment of peritoneal carcinomatosis in colorectal cancer is well established, following original randomized control trial by Verwaal et al. In patients with peritoneal cancer index less than six, 5-year survival approached 50% in a large retrospective series. Further, an Australian study of 611 patients demonstrated that cytoreductive surgery can be successfully performed in the elderly with equally good results. Of note, femoral nerve injuries are not uncommonly reported after pelvic surgery in around 2% of cases. As use of retractors has previously been associated with the risk of nerve compression or impingement, we have employed gentle manual retraction and followed precise anatomical planes. The most frequent manifestation of the involvement of the lumbosacral plexus or its branches with malignancy is lower back pain, referred leg pain and nerve palsies. Tumour may entrap the nerves either through direct invasion or via metastatic spread, either into the plexus itself or into the surrounding structures (iliacus and psoas muscles, or pelvic bones). In old cadaveric series, colon cancer was reported to be the most common cause of the malignancyrelated lumbosacral plexopathy, followed by sarcoma, breast cancer, Fig. 1. Tumour in situ in the right iliac fossa (bright white, measuring up to 5 cm in diameter – green arrow). Bowel mesentery is retracted medially (with assistant’s hands) and right pelvic sidewall is retracted laterally (with a retractor). Gonadal vessels are labelled with a blue arrow. Bladder is temporarily hitched to the skin (seen in the left lower corner on the picture). IMAGES FOR SURGEONS