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Special Feature
December 1, 2006

Image of the Month—Diagnosis

Arch Surg. 2006;141(12):1260. doi:10.1001/archsurg.141.12.1260

Answer: Retroperitoneal Schwannoma

Exploratory laparotomy revealed a mass, likely arising from the left adrenal gland, without any signs of infiltration of the pancreas (Figure 2). A left adrenalectomy was performed en bloc with the aforementioned lesion. At pathologic evaluation, the mass was clearly separated from the adrenal gland by a fibrous pseudocapsule. Results of histologic and immunohistochemical examination (intense staining for S100 using the alkaline phosphatase–anti–alkaline phosphatase method) were consistent with the diagnosis of schwannoma. At 65 months of follow-up, the patient was doing very well, with no signs of local or distant recurrence on a computed tomographic scan.

Figure 2. 
At surgical exploration, a 7-cm cystic mass was found in the upper left retroperitoneum, probably deriving from the left adrenal gland; the lesion was adjacent to the pancreas but did not infiltrate it.

At surgical exploration, a 7-cm cystic mass was found in the upper left retroperitoneum, probably deriving from the left adrenal gland; the lesion was adjacent to the pancreas but did not infiltrate it.

Schwannomas are a rare group of soft tissue tumors originating from the peripheral nerve sheath; they can occur anywhere neural tissue with Schwann cells is present, but most of them arise in the head and neck region or in the upper and lower extremities. Localization in deeper structures, such as the posterior mediastinum or retroperitoneum, is unusual. Retroperitoneal forms, in fact, account for only 0.7%-2.7% of all schwannomas1and 0.5%-1.2% of all retroperitoneal tumors.2Because of the flexibility of the retroperitoneum, tumors grow to a large size before becoming symptomatic. When apparent, clinical signs or symptoms are generally vague and nonspecific, as a consequence of adjacent organ compression or infiltration; therefore, detection is often accidental. Schwannoma typically appears as a solitary, well-encapsulated, firm, and smooth-surfaced round mass. In large tumors (>8-10 cm), a degenerative pattern (cystic areas, calcifications, interstitial fibrosis, and hyalinization) is commonly found that identifies the “ancient” variant.3

Retroperitoneal schwannomas generally have a benign biological behavior. Malignant forms usually develop ex novo because transformation of benign lesions is rather infrequent.4Whereas benign schwannomas tend to displace surrounding structures without invading them, malignant ones show the same biological features of undifferentiated sarcomas, with locally invasive growth and distant metastatic diffusion.

Preoperative diagnosis of retroperitoneal schwannomas is not easy owing to the difficulty in finding imaging features (with ultrasonography, computed tomography, or magnetic resonance imaging) that enable the discrimination of schwannomas from other soft-tissue tumors (fibrosarcoma or liposarcoma) and benign forms from malignant ones.5Schwannomas can frequently be misdiagnosed as psoas abscesses, pancreatic cysts or neoplasms, adnexal masses, or adrenal, kidney, or hepatic tumors, as reported in the literature.6-9However, radiologic imaging is helpful in therapeutic planning, as it gives information about the tumor's size, location, and possible invasion of other structures. Fine-needle aspiration biopsy may theoretically be useful if Schwann cells are found in the sample, but the tissue specimen collected for diagnosis is often inadequate and may be misleading because of cellular pleomorphism in degenerated areas, which might be interpreted as consistent with malignancy.10

Surgery is considered the best treatment for retroperitoneal schwannomas, as their response to radiation and chemotherapy is poor. Imaging, intraoperative macroscopic evaluation, and frozen section analysis are not valid or accurate indicators of malignancy, so a definitive diagnosis of the tumor's nature can be obtained only with a careful histologic and immunohistochemical examination. Considering the possibility of a misdiagnosed malignant lesion and a local recurrence rate of 10% to 20% also in benign schwannomas (probably due to incomplete excision), the optimal management should be a radical exeresis with clear margins, whenever feasible, eventually including in the resection adjacent structures.3,10After complete removal, long-term survival can be attained.

Box Section Ref ID


The Editor welcomes contributions to the “Image of the Month.” Manuscripts should be submitted via our online manuscript submission and review system (http://manuscripts.archsurg.com). Articles and photographs accepted will bear the contributor’s name. Manuscript criteria and information are per the “Instructions for Authors” for Archives of Surgery. No abstract is needed, and the manuscript should be no more than 3 typewritten pages. There should be a brief introduction, 1 multiple-choice question with 4 possible answers, and the main text. No more than 2 photographs should be submitted. There is no charge for reproduction and printing of color illustrations.

Correspondence:Antonio Pio Tortorelli, MD, Department of Surgical Sciences, Digestive Surgery Unit, Istituto di Clinica Chirurgica, Catholic University School of Medicine, Largo A. Gemelli, 8, 00168 Rome, Italy (dr_aragorn78@yahoo.it).

Accepted for Publication:November 23, 2005.

Author Contributions:Study concept and design: Tortorelli. Acquisition of data: Papa and Rosa. Analysis and interpretation of data: Pacelli and Doglietto. Drafting of the manuscript: Rosa. Critical revision of the manuscript for important intellectual content: Tortorelli, Papa, Pacelli, and Doglietto. Administrative, technical, and material support: Rosa. Study supervision: Tortorelli, Papa, Pacelli, and Doglietto.

Financial Disclosure:None reported.

Ueda  MOkamoto  YUeki  M A pelvic retroperitoneal schwannoma arising in the right paracolpium.  Gynecol Oncol 1996;60480- 483PubMedGoogle ScholarCrossref
Hayasaka  KTanaka  YSoeda  SHuppert  PClaussen  CD MR findings in primary retroperitoneal schwannoma.  Acta Radiol 1999;4078- 82PubMedGoogle ScholarCrossref
Giglio  MGiasotto  VMedica  M  et al.  Retroperitoneal ancient schwannoma: a case report and analysis of clinico-radiological findings.  Ann Urol (Paris) 2002;36104- 106PubMedGoogle ScholarCrossref
Rattier  BDesrousseaux  BDereux  HJAtat  IAmpe  J Benign retroperitoneal pelvic schwannoma: apropos of 2 cases [in French].  J Chir (Paris) 1990;127209- 212PubMedGoogle Scholar
Hughes  MJThomas  JMFisher  CMoskovic  EC Imaging features of retroperitoneal and pelvic schwannomas.  Clin Radiol 2005;60886- 893PubMedGoogle ScholarCrossref
Kishi  YKajiwara  SSeta  SKawauchi  NSuzuki  TSasaki  K Retroperitoneal schwannoma misdiagnosed as a psoas abscess: report of a case.  Surg Today 2002;32849- 852PubMedGoogle ScholarCrossref
Ibraheim  MIkomi  AKhan  F A pelvic retroperitoneal schwannoma mimicking an ovarian dermoid cyst in pregnancy.  J Obstet Gynaecol 2005;25620- 621PubMedGoogle ScholarCrossref
Duran  BGuvenal  TYildiz  ECetin  MErden  ODemirkoprulu  N An unusual cause of adnexal mass: fallopian tube schwannoma.  Gynecol Oncol 2004;92343- 346PubMedGoogle ScholarCrossref
Akiyoshi  TUeda  YYanai  K  et al.  Melanotic schwannoma of the pancreas: report of a case.  Surg Today 2004;34550- 553PubMedGoogle ScholarCrossref
Daneshmand  SYoussefzadeh  DChamie  K  et al.  Benign retroperitoneal schwannoma: a case series and review of the literature.  Urology 2003;62993- 997PubMedGoogle ScholarCrossref