Ann Thorac Surg 2001;72:1367-1369
© 2001 The Society of Thoracic Surgeons
Case report
Multilocular thymic cyst associated with Sjögren’s syndrome
Kazuya Kondo, MD, PhDa,
Takanori Miyoshi, MD, PhDa,
Syouji Sakiyama, MD, PhDa,
Yukio Shimosato, MD, PhDb,
Yasumasa Monden, MD, PhDa
a Second Department of Surgery, School of Medicine, University of Tokushima, Tokushima, Japan
b Department of Pathology, Keio University School of Medicine, Tokyo, Japan
Accepted for publication November 13, 2000.
Address reprint requests to Dr Kondo, Second Department of Surgery, School of Medicine, University of Tokushima, Kuramoto-cho, Tokushima, 770-8503, Japan
e-mail: kondo{at}clin.med.tokushima-u.ac.jp
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Abstract
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A 61-year-old woman, who had been diagnosed as having Sjögren’s syndrome, developed an anterior mediastinal mass. She was diagnosed with Sjögren’s syndrome with thymoma, preoperatively. Extended thymectomy was performed. Macroscopically, the mediastinal mass showed thick-walled multiloculated cavities filled with turbid yellow fluid. Microscopically, the cyst lining was continuous with thymic lobules in the wall with inflammatory process, cholesterol granuloma formation, and prominent lymph follicular hyperplasia. She was diagnosed with multilocular thymic cysts associated with Sjögren’s syndrome.
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Introduction
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Thymic cysts are relatively rare lesions (3% to 5% of anterior mediastinal masses) [1, 2]. They are commonly unilocular, and thin-walled. Some are characterized by multiloculation, thick fibrous walls, and coexistence of inflammation [1–4]. We encountered a case of multilocular thymic cyst (MTC) associated with Sjögren’s disease, and present its clinical and pathologic features.
A 61-year-old woman developed bilateral parotid swelling, dryness of the oral cavity, and itchy eyes that persisted for 4 months. She was diagnosed as having Sjögren’s syndrome, and was referred to our hospital for further work-up and treatment on April 23, 1998. Bilateral parotid glands were smooth-surfaced, enlarged, elastic hard, and not tender. Laboratory studies revealed elevation of rheumatoid factor (x 1,015) and anti-SS-A antibody (x 16). Chest computed tomography demonstrated anterior mediastinal mass shadow with areas of lower density (Fig 1). The patient was strongly suspected of Sjögren’s syndrome with thymoma. On June 15, 1998, extended thymectomy was performed. The mass did not show any adhesions to the adjacent mediastinal structures. Macroscopically, the cyst was 2.5 x 2.5 cm in size, and located in the central portion of the thymus. On cut section, the cyst showed multiloculated cavities with thick gray walls, and was filled with turbid yellow fluid. There were some smaller cysts around the main lesion (Fig 2). Microscopically, the cyst lining was continuous with thymic lobules in the wall. The cyst walls were fibrous, and exhibited intense, acute, and chronic inflammation with an admixture of neutrophils, plasma cells, small lymphocytes, and macrophages. Other areas showed extensive cholesterol granuloma formation with foreign body-type giant cells, and prominent lymph follicular hyperplasia with prominent germinal centers. The patient improved without steroid therapy, and was discharged on July 10, 1998. One year and 3 months later, the symptoms seen on admission to our hospital had disappeared.
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Fig 1. Chest computed tomography demonstrated anterior mediastinal mass shadow with areas of lower density.
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Fig 2. On cut section, the cyst measured 2.5 x 2.5 cm, and was located in the central portion of the thymus (arrowheads). The cyst showed multiloculated cavities with thick and gray walls, and was filled with turbid yellow fluid. There were some smaller cysts (arrows) around the main lesion.
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Comment
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MTC is a distinctive thymic lesion that morphologically and pathogenetically differs from congenital thymic cyst. The latter is usually unilocular, and lacks inflammatory processes. It is thin-walled, and contains serous fluid. Congenital thymic cyst is considered to arise as a congenital defect due to persistence of embryonal remnants [1, 2]. In contrast, MTC is always multilocular, and accompanied by inflammation. Its wall is thick and fibrous, and usually contains turbid fluid, as in this case. MTC is thought to be the result of an acquired cystic dilatation of the medullary duct against a background of inflammatory reaction of the thymic parenchyma [1, 3, 4].
Thymectomy is the required treatment of MTC for the following four reasons: (1) Preoperative diagnosis of MTC is difficult. We misdiagnosed MTC as thymoma, particularly thymoma with cystic degradation, preoperatively because of computed tomographic findings showing mediastinal solid density with areas of lower density, which were thought to be due to the presence of the thick fibrous wall and turbid fluid. (2) Intraoperative findings suggest its malignant nature. Although our case did not show adhesions to neighboring structures, the inflammatory process of MTC may frequently result in adhesions to surrounding mediastinal structures. This feature may mislead surgeons to suspect the malignant nature of the lesion at the time of surgery [4]. (3) MTC may recur postoperatively. Suster and Rosai reported that two of 24 MTCs recurred 2 and 4 years after excision, and that re-excision was successfully performed without evidence of disease 3 and 8 years later [3]. It is thought that the 2 recurrent cases may have been due to incomplete resection of multilocular cysts. (4) Thymic epithelial tumor may coexist with MTC. Suster and Rosai reported that 4 of 24 cases had an incidental thymic epithelial tumor (thymoma, 2 cases; basaloid carcinoma, 2 cases) within the wall of the cyst [3]. Thorough and careful examination of the resected thymus including cysts is of the utmost importance. When the lesion is diagnosed as MTC, postoperative irradiation or chemotherapy is not necessary.
MTC occasionally involves autoimmune disease. Our case was complicated with Sjögren’s syndrome, and was treated by extended thymectomy. Suster and colleagues reported 2 cases of MTC with Sjögren’s syndrome, 1 with aplastic anemia, 1 with chronic myeloid leukemia, 1 with Duncan’s syndrome (X-linked lymphoproliferative disease), and 1 with acquired immunodeficiency syndrome [3, 4]. Avila and associates reported that MTC occurred in children with human immunodeficiency virus infection, although the incidence of MTC in such patients was rare (4 of 440) at their institution [5]. MTC is thought to be derived from an acquired inflammatory process [1, 3, 4]. However, further investigation of the systemic background of MTC may be necessary, because MTC is a complication of the various diseases described above, including autoimmune and neoplastic diseases.
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References
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Shimosato Y., Mukai K. Tumor of the mediastinum. In: Rosai J., ed. Atlas of tumor pathology, 3rd series. Fascicle 2. Washington, DC: Armed Forces Institute of Pathology, 1997:233-237.
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Rosai J., Levine G.D. Tumor of the thymus. In: Firminger H.I., ed. Atlas of tumor pathology, 2nd series. Fascicle 13. Washington, DC: Armed Forces Institute of Pathology, 1976:207-211.
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Suster S., Rosai J. Multilocular thymic cyst: an acquired reactive process study of 18 cases. Am J Surg Pathol 1991;15:388-398.[Medline]
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Suster S., Barbuto D., Carlson G., et al. Multilocular thymic cysts with pseudoepitheliomatous hyperplasia. Hum Pathol 1991;22:455-460.[Medline]
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Avila N.A., Mueller B.U., Carrasquillo J.A., et al. Multilocular thymic cysts: imaging features in children with human immunodeficiency virus infection. Radiology 1996;201:130-134.[Abstract/Free Full Text]
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Abstract
Introduction
