Sacral Amputation for Sarcoma: Case Report
Roger Hartl, MD
Robert J. Standerfer, MD*
Stephen W. Coons, MD**
Curtis A. Dickman, MD
Divisions of Neurological Surgery and **Neuropathology, Barrow Neurological Institute, and *Department of Surgery, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
Tumors of the sacrum are rare, and malignant sacral lesions such as sarcomas typically are associated with a poor prognosis. Radical surgical resection is the mainstay of treatment followed by radiation therapy and sometimes chemotherapy. Resection of these lesions can be challenging because the anatomy of this region is complex and nervous and vascular structures are frequently involved. We report a patient with a malignant peripheral nerve sheath tumor in the sacrum who underwent subtotal sacrectomy; stability of the sacroiliac joint was maintained through anterior and posterior approaches performed during the same operative setting. The patient's motor function was preserved. A multidisciplinary approach involving the neurosurgeon, colorectal surgeon, and plastic surgeon in the operating room and the oncologist and radiation oncologist in the postoperative period is key to the successful and expedient treatment of these lesions.
Key Words: malignant peripheral nerve sheath tumor, sacrectomy, sacrum, sarcoma
Tumors of the sacrum are rare and encompass a variety of lesions, including congenital lesions, inflammatory masses, neurogenic and osseous tumors, metastatic lesions, and others such as aneurysmal bone cysts and sarcomas.[18-20,30] Primary malignant sacral bony lesions, which include Ewing's sarcomas, osteosarcomas, and chondrosarcomas, are associated with a poor prognosis.[3,5,9,15,26] Aggressive surgical resection is the mainstay of treatment followed by radiation of the surgical bed and sometimes adjuvant chemotherapy. Resection of these lesions is difficult because the anatomy of this region is complex and neurovascular structures are often involved. Because tumors of the sacrum are rare, few institutions have large series of patients who have undergone en bloc resection of these lesions. [19,30] Hence, experience regarding the optimum surgical technique and indications for the resection of sacral tumors is limited.
We present a patient who underwent a sacral laminectomy for treatment of a lesion thought to be a benign nerve sheath tumor but that was diagnosed as a malignant sarcoma after partial resection. The patient then underwent a sacral amputation and en bloc resection of the remaining tumor. This case illustrates a surgical technique for subtotal sacrectomy that maintains stability of the sacroiliac joint. A multidisciplinary approach involving a neurosurgeon, vascular surgeon, colorectal surgeon, and plastic surgeon during surgery and an oncologist and radiation oncologist after surgery is key to aggressive treatment of these lesions.
A 49-year-old, previously healthy man was referred for evaluation of a tumor at S2 on the right. Six months earlier he had noticed aching pain in his tailbone radiating down the posterior aspect of his right leg into his foot. Numbness across his right buttock; down his posterior right leg to the foot; and on the right side of his scrotum, penis, and anus followed. He also experienced some sexual dysfunction and urinary urgency.
On physical examination the patient was well nourished, had stable vital signs, and appeared to be in good health. His motor strength was 5/5 in all extremities, and the straight leg sign was negative. There was no tenderness along his lower lumbar spine, hips, or sacroiliac joint. Pinprick sensation was diminished along the dorsum of the right foot and medial aspect of the calf. His right ankle jerk was absent; all other reflexes were 2+.
Figure 1. Preoperative magnetic resonance images show an S2 lesion on the right and expansion of the neural foramen.
Magnetic resonance imaging of the lumbar spine and sacrum showed a 3-cm enhancing mass involving the right S2 nerve root and extending into the sacrum and S2 neural foramen (Fig. 1). Based on these images, a nerve sheath tumor was diagnosed. The patient underwent a sacral laminectomy for resection of the tumor. A firm, encapsulated, gray-tan, extradural mass appeared to be infiltrating the S2 nerve root, which was thickened. Subtotal resection was achieved, and the S2 nerve root was preserved.
Figure 2. (A) The tumor was composed of fascicles of atypical spindle cells and scattered large bizarre cells. (Hematoxylin and eosin; original magnification, x400). (B) S-100 positive Schwann cells in the S2 nerve root are infiltrated and surrounded by tumor cells that are negative for S-100. (S-100 with diaminobenzidine and hematoxylin; original magnification , x200).
Microscopic examination showed a highly cellular neoplasm composed of spindle cells and large bizarre cells with atypia, pleomorphism, and a high mitotic rate. The neoplastic cells had infiltrated and spread extensively within the S2 nerve root (Fig. 2). The neoplastic cells were negative for S-100, desmin, keratin AE1/AE3, and epithelial membrane antigen. Based on these characteristics, a high-grade sarcoma was diagnosed. The growth pattern was most consistent with a malignant peripheral nerve sheath tumor (MPNST).