Bilateral Granular Cell Tumors of the Posterior Mediastinum Seena C . Aisner, M.D., Ashish K. Chakravarthy, M.D., John N. Joslyn, M.D., and Thomas R. Coughlin, M.D. ABSTRACT Granular cell tumors are uncommon and generally benign lesions that are commonly accepted to be of Schwann cell origin. These tumors occur most frequently in the skin and oral cavity and are generally asymptomatic. However, when signs and symptoms occur, they are relative to the organ or site involved. The histological features are distinct. Surgical resection is curative in almost all cases, with only rare local recurrences. We report a case of symptomatic bilateral granular cell tumors arising in the posterior mediastinum.
A 27-year-old woman with a 3-year history of chest pain had had a chronic unrelenting cough for one month. She denied shortness of breath, wheezing, dizziness, sweating, chills, or fever. The patient was admitted to the University of Maryland Hospital on May 25, 1987. Results of physical examination and laboratory studies were normal. Chest roentgenograms (Fig 1) showed bilateral apical, posterior mediastinal masses. Computed tomography and magnetic resonance imaging scans showed them to be located extrapleurally (Fig 2). The left transaxillary thopatient underwent an racotomy on May 26, 1987. A firm, tan, incompletely circumscribed tumor was found in the left apex attached to the sympathetic chain and overlying the parietal pleura. The tumor was completely excised from the sympathetic chain ganglion and nerve. Postoperatively left Horner’s syndrome developed. Three weeks after her initial operation, the patient had a right thoracotomy to remove a similar neoplasm attached to the posterior sympathetic chain. Except for persistent left Horner’s syndrome, the patient had an uneventful recovery with resolution of her pulmonary symptoms and she was discharged on June 19,1987. At 12 months‘ follow-up, the patient remains asymptomatic with resolution of her Horner’s syndrome.
Fig I . Posteroanterior chest roentgenogram revealing bilateral apical, posterior mediustinal musses (arrows).
Pathology Both of the excised tumors were grossly similar, each being 4.0-cm in diameter, circumscribed, firm, tan, and solid. Microscopic examination showed the tumors conFrom the Department of Pathology, Radiology, and Surgery, University of Maryland School of Medicine, Baltimore, MD. Accepted for publication July 28, 1988. Address reprint requests to Dr.Aisner, Department of Pathology, University of Maryland School of Medicine, 10 South Pine St, Baltimore, MD 21201.
Fig 2. Axid Ti-weighted magnetic resonance imaging scan demonstrating homogeneous bilateral paravertebral musses (arrows).
688 Ann Thorac Surg 46688-689, Dec 1988. Copyright 0 1988 by The Society of Thoracic Surgeons
689 Case Report: Aisner et al: Mediastinal Granular Cell Tumors
Fig 3. Granular cell tumor showing finely granular cytoplasm and small hyperchromatic nuclei. Note single round ganglion cell (arrow). ( H 6 E ; ~ 4 2 before 0 38% reduction.)
sisted of granular cells with remnants of sympathetic nerve and ganglion (Fig 3). These tumor cells were large, round to polygonal cells with finely granular cytoplasm and small hyperchromatic nuclei and lacked pleomorphism or mitotic figures. Staining showed diastaseresistant, periodic acid-Schiff-positive material in the cytoplasm. Immunoperoxidase staining for S-100 protein on paraffin sections demonstrated positive cytoplasmic reactivity in all cells. Electron microscopic examination on buffered formalin-fixed material showed subcompartmentalization of each cell into distinct limiting membranes containing occasional electron-dense inclusions. These findings are typical of this tumor regardless of its site of origin [l].
Comment Various attempts at identifying the histogenesis of granular cell tumors have not completely eliminated the controversies as to its cell of origin. While early descriptions by Abrikossoff  likened this neoplasm to embryonal skeletal muscle, most authors have not shared this view. Fust and Custer  found a close relationship of this tumor to peripheral nerves, supporting a neural origin. Since then, most evidence has supported this theory. Electron microscopy studies conducted by Fisher and Wechsler  and later ones by Mackay and associates [ l ] led to the conclusion that nerve was the most likely tissue of origin but electron microscopy studies could not confirm the histogenesis of the tumor. Recent electron microscopy studies by Khansur and associates  also were unable to positively identify this tumor as schwannian in origin. However, by identifying desmo-
somes, these authors effectivelyruled out a histiocytic or myogenous origin. Supporting evidence for a Schwann cell origin has been detection of the neuroectodermal protein, S-100, in these tumors [ 6 ] .The granular cell tumor in our case also demonstrated S-100 positivity. S-100 is an acidic protein found in neural cells, neural tumors, and melanocytes. Granular cell tumors are ubiquitous and occur most commonly in the skin, subcutis, and oral cavity . Visceral sites including the bronchus  have also been described. Extrapleural thoracic sites have not been reported to the best of our knowledge. In our patient the location of these tumors in the apical posterior mediastinum is in keeping with other neural neoplasms that arise most commonly in the posterior mediastinum, such as schwannomas, neurofibromas, and ganglioneuromas. Recurrence after excision in any site is rare . Large tumors (greater than 5 cm in diameter), a rapid growth rate, and invasion of adjacent structures may suggest malignant behavior . Complete excision of thoracic tumors may be the best method of treatment. Accurate frozen section diagnosis will influence the surgical approach chosen to excise granular cell tumors in the thoracic cavity, thus avoiding multiple operations. We wish to acknowledge Perry Comegys for his photographic assistance. We also wish to acknowledge the editor and reviewers for their excellent review and assistance in the preparation of this paper.
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