Ancient Schwannoma, though benign, can cause diagnostic dilemma because of its clinical presentation and imaging features. We report the management of a giant retroperitoneal schwannoma in a 19-year-old young lady who presented with lower abdominal distension. CT scan reported a large heterogenous lesion in the abdominopelvic retroperitoneum (42？cm × 16？cm × 16？cm) as a malignant tumor. The unique problems we encountered were the enormous size, the location of major part of the tumor in the pelvis, the need for fertility preservation, the external iliac vessels stretching over the tumor making mobilization surgically demanding, and the prospects of neurological deficits. An en bloc resection of schwannoma with common iliac, external iliac and internal iliac veins, internal iliac artery, femoral and obturator nerves, and iliopsoas muscle was done maintaining oncological principles. External iliac artery that was cut to facilitate tumor mobilization was reanastomosed at the end of the procedure. Postoperatively patient had uneventful recovery with patchy sensory loss, foot drop, and quadriceps weakness which was rehabilitated with a foot drop splint and active physiotherapy. 1. Introduction Giant retroperitoneal schwannoma, though benign, can cause diagnostic dilemma because of its clinical presentation and imaging features. In addition, it is a surgical challenge due to its enormous size and proximity to large vessels and other organs in the retroperitoneum. We are presenting a case, probably one of the largest retroperitoneal schwannomas reported in English medical literature, to discuss the unique surgical problems encountered in the management. The importance of proper anatomical localization of vessels, preoperative planning, and optimal involvement of specialists of other subspecialties for effective resection is reiterated. 2. Case Presentation 19-year-old postmenarchal young lady presented with lower abdominal distention and neuritic type of pain in the right thigh of two-year duration. The lower abdominal distension was progressively increasing and was associated with an increasing pain in the leg as described. There were no neurological symptoms. Clinically she had ECOG performance status 1, antalgic gait, and lower abdominal distension up to umbilicus with a firm to hard fixed mass arising from the pelvis. There were no neurocutaneous markers. Computed tomography study revealed a large lobulated heterogeneously enhancing mass lesion in the pelvic retroperitoneum (craniocaudal measurement 42？cm, anteroposterior measurement 16？cm, and transverse
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